diff --git a/DEPS b/DEPS
index 543745e527f..2a7474080bd 100644
--- a/DEPS
+++ b/DEPS
@@ -56,7 +56,7 @@ vars = {
   # Revisions of /third_party/* dependencies.
   "args_tag": "1.5.0",
   "async_tag": "2.0.8",
-  "bazel_worker_tag": "bazel_worker-v0.1.20",
+  "bazel_worker_tag": "v0.1.22",
   "benchmark_harness_tag": "81641290dea44c34138a109a37e215482f405f81",
   "boolean_selector_tag" : "1.0.4",
   "boringssl_gen_rev": "b9e27cff1ff0803e97ab1f88764a83be4aa94a6d",
@@ -117,7 +117,7 @@ vars = {
   "pedantic_tag": "v1.8.0",
   "ply_rev": "604b32590ffad5cbb82e4afef1d305512d06ae93",
   "pool_tag": "1.3.6",
-  "protobuf_rev": "7d34c9e4e552a4f66acce32e4344ae27756a1949",
+  "protobuf_rev": "3746c8fd3f2b0147623a8e3db89c3ff4330de760",
   "pub_rev": "df0f72daaa724e29ed6075e0fb5549a6d6dc5daf",
   "pub_semver_tag": "1.4.2",
   "quiver-dart_tag": "2.0.0+1",
@@ -342,7 +342,7 @@ deps = {
   Var("dart_root") + "/third_party/pkg/pool":
       Var("dart_git") + "pool.git" + "@" + Var("pool_tag"),
   Var("dart_root") + "/third_party/pkg/protobuf":
-      Var("dart_git") + "protobuf.git" + "@" + Var("protobuf_rev"),
+       Var("dart_git") + "protobuf.git" + "@" + Var("protobuf_rev"),
   Var("dart_root") + "/third_party/pkg/pub_semver":
       Var("dart_git") + "pub_semver.git" + "@" + Var("pub_semver_tag"),
   Var("dart_root") + "/third_party/pkg/pub":
diff --git a/pkg/vm/lib/transformations/protobuf_aware_treeshaker/transformer.dart b/pkg/vm/lib/transformations/protobuf_aware_treeshaker/transformer.dart
index 7da31945ae5..b00cca1a728 100644
--- a/pkg/vm/lib/transformations/protobuf_aware_treeshaker/transformer.dart
+++ b/pkg/vm/lib/transformations/protobuf_aware_treeshaker/transformer.dart
@@ -62,6 +62,9 @@ InfoCollector removeUnusedProtoReferences(
   final gmClass = protobufLib.classes
       .where((klass) => klass.name == 'GeneratedMessage')
       .single;
+  final tagNumberClass =
+      protobufLib.classes.where((klass) => klass.name == 'TagNumber').single;
+
   final collector = InfoCollector(gmClass);
 
   final biClass =
@@ -71,8 +74,8 @@ InfoCollector removeUnusedProtoReferences(
 
   component.accept(collector);
 
-  _UnusedFieldMetadataPruner(
-          biClass, addMethod, collector.dynamicSelectors, coreTypes, info)
+  _UnusedFieldMetadataPruner(tagNumberClass, biClass, addMethod,
+          collector.dynamicSelectors, coreTypes, info)
       .removeMetadataForUnusedFields(
     collector.gmSubclasses,
     collector.gmSubclassesInvokedMethods,
@@ -85,6 +88,8 @@ InfoCollector removeUnusedProtoReferences(
 
 /// For protobuf fields which are not accessed, prune away its metadata.
 class _UnusedFieldMetadataPruner extends TreeVisitor<void> {
+  final Class tagNumberClass;
+  final Reference tagNumberField;
   // All of those methods have the dart field name as second positional
   // parameter.
   // Method names are defined in:
@@ -93,26 +98,34 @@ class _UnusedFieldMetadataPruner extends TreeVisitor<void> {
   // https://github.com/dart-lang/protobuf/blob/master/protoc_plugin/lib/protobuf_field.dart.
   static final fieldAddingMethods = Set<String>.from(const <String>[
     'a',
-    'm',
-    'pp',
-    'pc',
-    'e',
-    'pc',
+    'aOM',
     'aOS',
+    'aQM',
+    'pPS',
+    'aQS',
+    'aInt64',
     'aOB',
+    'e',
+    'p',
+    'pc',
+    'm',
   ]);
 
   final Class builderInfoClass;
   Class visitedClass;
   final names = Set<String>();
+  final usedTagNumbers = Set<int>();
 
   final dynamicNames = Set<String>();
   final CoreTypes coreTypes;
   final TransformationInfo info;
   final Member addMethod;
 
-  _UnusedFieldMetadataPruner(this.builderInfoClass, this.addMethod,
-      Set<Selector> dynamicSelectors, this.coreTypes, this.info) {
+  _UnusedFieldMetadataPruner(this.tagNumberClass, this.builderInfoClass,
+      this.addMethod, Set<Selector> dynamicSelectors, this.coreTypes, this.info)
+      : tagNumberField = tagNumberClass.fields
+            .firstWhere((f) => f.name.name == 'tagNumber')
+            .reference {
     dynamicNames.addAll(dynamicSelectors.map((sel) => sel.target.name));
   }
 
@@ -140,30 +153,58 @@ class _UnusedFieldMetadataPruner extends TreeVisitor<void> {
     names.clear();
     names.addAll(selectors.map((sel) => sel.target.name));
     visitedClass = gmSubclass;
+    _computeUsedTagNumbers(gmSubclass);
     field.initializer.accept(this);
   }
 
+  void _computeUsedTagNumbers(Class gmSubclass) {
+    usedTagNumbers.clear();
+    for (final procedure in gmSubclass.procedures) {
+      for (final annotation in procedure.annotations) {
+        if (annotation is ConstantExpression) {
+          final constant = annotation.constant;
+          if (constant is InstanceConstant &&
+              constant.classReference == tagNumberClass.reference) {
+            final name = procedure.canonicalName.name;
+            if (dynamicNames.contains(name) || names.contains(name)) {
+              usedTagNumbers.add(
+                  (constant.fieldValues[tagNumberField] as IntConstant).value);
+            }
+          }
+        }
+      }
+    }
+  }
+
   @override
   visitLet(Let node) {
+    // The BuilderInfo field `_i` is set up with a row of cascaded calls.
+    // ```
+    // static final BuilderInfo _i = BuilderInfo('MessageName')
+    //     ..a(1, 'foo', PbFieldType.OM)
+    //     ..a(2, 'bar', PbFieldType.OM)
+    // ```
+    // Each cascaded call will be represented in kernel as a let, where the
+    // initializer will be a call to a method of `builderInfo`. For example:
+    // ```
+    // {protobuf::BuilderInfo::a}<dart.core::int*>(1, "foo", #C10)
+    // ```
+    // The methods enumerated in `fieldAddingMethods` are the ones that set up
+    // fields (other methods do other things).
+    //
+    // First argument is the tag-number of the added field.
+    // Second argument is the field-name.
+    // Further arguments are specific to the method.
     final initializer = node.variable.initializer;
     if (initializer is MethodInvocation &&
         initializer.interfaceTarget?.enclosingClass == builderInfoClass &&
         fieldAddingMethods.contains(initializer.name.name)) {
-      final fieldName =
-          (initializer.arguments.positional[1] as StringLiteral).value;
-      final ucase = fieldName[0].toUpperCase() + fieldName.substring(1);
-      // The name of the related `clear` method.
-      final clearName = 'clear${ucase}';
-      // The name of the related `has` method.
-      final hasName = 'has${ucase}';
-
-      bool nameIsUsed(String name) =>
-          dynamicNames.contains(name) || names.contains(name);
-
-      if (!(nameIsUsed(fieldName) ||
-          nameIsUsed(clearName) ||
-          nameIsUsed(hasName))) {
+      final tagNumber =
+          (initializer.arguments.positional[0] as IntLiteral).value;
+      if (!usedTagNumbers.contains(tagNumber)) {
         if (info != null) {
+          final fieldName =
+              (initializer.arguments.positional[1] as StringLiteral).value;
           info.removedMessageFields.add("${visitedClass.name}.$fieldName");
         }
 
diff --git a/pkg/vm/test/transformations/protobuf_aware_treeshaker/treeshaker_test.dart b/pkg/vm/test/transformations/protobuf_aware_treeshaker/treeshaker_test.dart
index 7734f54d3ea..2b2397ac6cb 100644
--- a/pkg/vm/test/transformations/protobuf_aware_treeshaker/treeshaker_test.dart
+++ b/pkg/vm/test/transformations/protobuf_aware_treeshaker/treeshaker_test.dart
@@ -36,7 +36,8 @@ runTestCase(Uri source) async {
 
   for (Class messageClass in messageClasses) {
     expect(messageClass.enclosingLibrary.classes.contains(messageClass),
-        messageClass.name.endsWith('Keep'));
+        messageClass.name.endsWith('Keep'),
+        reason: '$messageClass');
   }
 
   final systemTempDir = Directory.systemTemp;
@@ -50,8 +51,8 @@ runTestCase(Uri source) async {
     printer.writeComponentFile(component);
     await sink.close();
 
-    ProcessResult result =
-        Process.runSync(Platform.resolvedExecutable, [file.path]);
+    final result = Process.runSync(
+        Platform.resolvedExecutable, ['--enable-asserts', file.path]);
     expect(result.exitCode, 0, reason: '${result.stderr}\n${result.stdout}');
   } finally {
     if (file.existsSync()) {
diff --git a/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/compile_protos.sh b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/compile_protos.sh
index b4793eec240..8031891c8b7 100755
--- a/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/compile_protos.sh
+++ b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/compile_protos.sh
@@ -5,11 +5,12 @@
 
 # Running this script requires having protoc_plugin installed in your path.
 
-rm -rf lib/generated
-mkdir lib/generated
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
+
+rm -rf $DIR/lib/generated
+mkdir $DIR/lib/generated
 
 # Directory of the script
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
 GENERATED_DIR=$DIR/lib/generated
 
 protoc --dart_out=$GENERATED_DIR -I$DIR/protos $DIR/protos/*.proto
diff --git a/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/lib/generated/foo.pb.dart b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/lib/generated/foo.pb.dart
index 406377357da..cab78838e29 100644
--- a/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/lib/generated/foo.pb.dart
+++ b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/lib/generated/foo.pb.dart
@@ -1,253 +1,345 @@
 ///
 //  Generated code. Do not modify.
 //  source: foo.proto
-///
-// ignore_for_file: non_constant_identifier_names,library_prefixes,unused_import
+//
+// @dart = 2.3
+// ignore_for_file: camel_case_types,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type
 
-// ignore: UNUSED_SHOWN_NAME
-import 'dart:core' show int, bool, double, String, List, Map, override;
+import 'dart:core' as $core;
 
 import 'package:protobuf/protobuf.dart' as $pb;
 
 class FooKeep extends $pb.GeneratedMessage {
-  static final $pb.BuilderInfo _i = new $pb.BuilderInfo('FooKeep')
-    ..a<BarKeep>(
-        1, 'barKeep', $pb.PbFieldType.OM, BarKeep.getDefault, BarKeep.create)
-    ..a<BarKeep>(
-        2, 'barDrop', $pb.PbFieldType.OM, BarKeep.getDefault, BarKeep.create)
-    ..m<String, BarKeep>(3, 'mapKeep', 'FooKeep.MapKeepEntry',
-        $pb.PbFieldType.OS, $pb.PbFieldType.OM, BarKeep.create, null, null)
-    ..m<String, ZopDrop>(4, 'mapDrop', 'FooKeep.MapDropEntry',
-        $pb.PbFieldType.OS, $pb.PbFieldType.OM, ZopDrop.create, null, null)
-    ..a<int>(5, 'aKeep', $pb.PbFieldType.O3)
-    ..a<HasKeep>(
-        6, 'hasKeep', $pb.PbFieldType.OM, HasKeep.getDefault, HasKeep.create)
-    ..a<ClearKeep>(7, 'clearKeep', $pb.PbFieldType.OM, ClearKeep.getDefault,
-        ClearKeep.create)
-    ..hasRequiredFields = false;
+  static final $pb.BuilderInfo _i =
+      $pb.BuilderInfo('FooKeep', createEmptyInstance: create)
+        ..aOM<BarKeep>(1, 'barKeep',
+            protoName: 'barKeep', subBuilder: BarKeep.create)
+        ..aOM<BarKeep>(2, 'barDrop',
+            protoName: 'barDrop', subBuilder: BarKeep.create)
+        ..m<$core.String, BarKeep>(3, 'mapKeep',
+            protoName: 'mapKeep',
+            entryClassName: 'FooKeep.MapKeepEntry',
+            keyFieldType: $pb.PbFieldType.OS,
+            valueFieldType: $pb.PbFieldType.OM,
+            valueCreator: BarKeep.create)
+        ..m<$core.String, ZopDrop>(4, 'mapDrop',
+            protoName: 'mapDrop',
+            entryClassName: 'FooKeep.MapDropEntry',
+            keyFieldType: $pb.PbFieldType.OS,
+            valueFieldType: $pb.PbFieldType.OM,
+            valueCreator: ZopDrop.create)
+        ..a<$core.int>(5, 'aKeep', $pb.PbFieldType.O3, protoName: 'aKeep')
+        ..aOM<HasKeep>(6, 'hasKeep',
+            protoName: 'hasKeep', subBuilder: HasKeep.create)
+        ..aOM<ClearKeep>(7, 'clearKeep',
+            protoName: 'clearKeep', subBuilder: ClearKeep.create)
+        ..hasRequiredFields = false;
 
-  FooKeep() : super();
-  FooKeep.fromBuffer(List<int> i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromBuffer(i, r);
-  FooKeep.fromJson(String i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromJson(i, r);
-  FooKeep clone() => new FooKeep()..mergeFromMessage(this);
+  FooKeep._() : super();
+  factory FooKeep() => create();
+  factory FooKeep.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory FooKeep.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  FooKeep clone() => FooKeep()..mergeFromMessage(this);
   FooKeep copyWith(void Function(FooKeep) updates) =>
       super.copyWith((message) => updates(message as FooKeep));
   $pb.BuilderInfo get info_ => _i;
-  static FooKeep create() => new FooKeep();
+  @$core.pragma('dart2js:noInline')
+  static FooKeep create() => FooKeep._();
   FooKeep createEmptyInstance() => create();
-  static $pb.PbList<FooKeep> createRepeated() => new $pb.PbList<FooKeep>();
-  static FooKeep getDefault() => _defaultInstance ??= create()..freeze();
+  static $pb.PbList<FooKeep> createRepeated() => $pb.PbList<FooKeep>();
+  @$core.pragma('dart2js:noInline')
+  static FooKeep getDefault() =>
+      _defaultInstance ??= $pb.GeneratedMessage.$_defaultFor<FooKeep>(create);
   static FooKeep _defaultInstance;
 
+  @$pb.TagNumber(1)
   BarKeep get barKeep => $_getN(0);
+  @$pb.TagNumber(1)
   set barKeep(BarKeep v) {
     setField(1, v);
   }
 
-  bool hasBarKeep() => $_has(0);
+  @$pb.TagNumber(1)
+  $core.bool hasBarKeep() => $_has(0);
+  @$pb.TagNumber(1)
   void clearBarKeep() => clearField(1);
+  @$pb.TagNumber(1)
+  BarKeep ensureBarKeep() => $_ensure(0);
 
+  @$pb.TagNumber(2)
   BarKeep get barDrop => $_getN(1);
+  @$pb.TagNumber(2)
   set barDrop(BarKeep v) {
     setField(2, v);
   }
 
-  bool hasBarDrop() => $_has(1);
+  @$pb.TagNumber(2)
+  $core.bool hasBarDrop() => $_has(1);
+  @$pb.TagNumber(2)
   void clearBarDrop() => clearField(2);
+  @$pb.TagNumber(2)
+  BarKeep ensureBarDrop() => $_ensure(1);
 
-  Map<String, BarKeep> get mapKeep => $_getMap(2);
+  @$pb.TagNumber(3)
+  $core.Map<$core.String, BarKeep> get mapKeep => $_getMap(2);
 
-  Map<String, ZopDrop> get mapDrop => $_getMap(3);
+  @$pb.TagNumber(4)
+  $core.Map<$core.String, ZopDrop> get mapDrop => $_getMap(3);
 
-  int get aKeep => $_get(4, 0);
-  set aKeep(int v) {
+  @$pb.TagNumber(5)
+  $core.int get aKeep => $_getIZ(4);
+  @$pb.TagNumber(5)
+  set aKeep($core.int v) {
     $_setSignedInt32(4, v);
   }
 
-  bool hasAKeep() => $_has(4);
+  @$pb.TagNumber(5)
+  $core.bool hasAKeep() => $_has(4);
+  @$pb.TagNumber(5)
   void clearAKeep() => clearField(5);
 
+  @$pb.TagNumber(6)
   HasKeep get hasKeep => $_getN(5);
+  @$pb.TagNumber(6)
   set hasKeep(HasKeep v) {
     setField(6, v);
   }
 
-  bool hasHasKeep() => $_has(5);
+  @$pb.TagNumber(6)
+  $core.bool hasHasKeep() => $_has(5);
+  @$pb.TagNumber(6)
   void clearHasKeep() => clearField(6);
+  @$pb.TagNumber(6)
+  HasKeep ensureHasKeep() => $_ensure(5);
 
+  @$pb.TagNumber(7)
   ClearKeep get clearKeep => $_getN(6);
+  @$pb.TagNumber(7)
   set clearKeep(ClearKeep v) {
     setField(7, v);
   }
 
-  bool hasClearKeep() => $_has(6);
+  @$pb.TagNumber(7)
+  $core.bool hasClearKeep() => $_has(6);
+  @$pb.TagNumber(7)
   void clearClearKeep() => clearField(7);
+  @$pb.TagNumber(7)
+  ClearKeep ensureClearKeep() => $_ensure(6);
 }
 
 class BarKeep extends $pb.GeneratedMessage {
-  static final $pb.BuilderInfo _i = new $pb.BuilderInfo('BarKeep')
-    ..a<int>(1, 'aKeep', $pb.PbFieldType.O3)
-    ..a<int>(2, 'bDrop', $pb.PbFieldType.O3)
-    ..hasRequiredFields = false;
+  static final $pb.BuilderInfo _i =
+      $pb.BuilderInfo('BarKeep', createEmptyInstance: create)
+        ..a<$core.int>(1, 'aKeep', $pb.PbFieldType.O3, protoName: 'aKeep')
+        ..a<$core.int>(2, 'bDrop', $pb.PbFieldType.O3, protoName: 'bDrop')
+        ..hasRequiredFields = false;
 
-  BarKeep() : super();
-  BarKeep.fromBuffer(List<int> i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromBuffer(i, r);
-  BarKeep.fromJson(String i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromJson(i, r);
-  BarKeep clone() => new BarKeep()..mergeFromMessage(this);
+  BarKeep._() : super();
+  factory BarKeep() => create();
+  factory BarKeep.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory BarKeep.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  BarKeep clone() => BarKeep()..mergeFromMessage(this);
   BarKeep copyWith(void Function(BarKeep) updates) =>
       super.copyWith((message) => updates(message as BarKeep));
   $pb.BuilderInfo get info_ => _i;
-  static BarKeep create() => new BarKeep();
+  @$core.pragma('dart2js:noInline')
+  static BarKeep create() => BarKeep._();
   BarKeep createEmptyInstance() => create();
-  static $pb.PbList<BarKeep> createRepeated() => new $pb.PbList<BarKeep>();
-  static BarKeep getDefault() => _defaultInstance ??= create()..freeze();
+  static $pb.PbList<BarKeep> createRepeated() => $pb.PbList<BarKeep>();
+  @$core.pragma('dart2js:noInline')
+  static BarKeep getDefault() =>
+      _defaultInstance ??= $pb.GeneratedMessage.$_defaultFor<BarKeep>(create);
   static BarKeep _defaultInstance;
 
-  int get aKeep => $_get(0, 0);
-  set aKeep(int v) {
+  @$pb.TagNumber(1)
+  $core.int get aKeep => $_getIZ(0);
+  @$pb.TagNumber(1)
+  set aKeep($core.int v) {
     $_setSignedInt32(0, v);
   }
 
-  bool hasAKeep() => $_has(0);
+  @$pb.TagNumber(1)
+  $core.bool hasAKeep() => $_has(0);
+  @$pb.TagNumber(1)
   void clearAKeep() => clearField(1);
 
-  int get bDrop => $_get(1, 0);
-  set bDrop(int v) {
+  @$pb.TagNumber(2)
+  $core.int get bDrop => $_getIZ(1);
+  @$pb.TagNumber(2)
+  set bDrop($core.int v) {
     $_setSignedInt32(1, v);
   }
 
-  bool hasBDrop() => $_has(1);
+  @$pb.TagNumber(2)
+  $core.bool hasBDrop() => $_has(1);
+  @$pb.TagNumber(2)
   void clearBDrop() => clearField(2);
 }
 
 class HasKeep extends $pb.GeneratedMessage {
-  static final $pb.BuilderInfo _i = new $pb.BuilderInfo('HasKeep')
-    ..a<int>(1, 'aDrop', $pb.PbFieldType.O3)
-    ..hasRequiredFields = false;
+  static final $pb.BuilderInfo _i =
+      $pb.BuilderInfo('HasKeep', createEmptyInstance: create)
+        ..a<$core.int>(1, 'aDrop', $pb.PbFieldType.O3, protoName: 'aDrop')
+        ..hasRequiredFields = false;
 
-  HasKeep() : super();
-  HasKeep.fromBuffer(List<int> i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromBuffer(i, r);
-  HasKeep.fromJson(String i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromJson(i, r);
-  HasKeep clone() => new HasKeep()..mergeFromMessage(this);
+  HasKeep._() : super();
+  factory HasKeep() => create();
+  factory HasKeep.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory HasKeep.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  HasKeep clone() => HasKeep()..mergeFromMessage(this);
   HasKeep copyWith(void Function(HasKeep) updates) =>
       super.copyWith((message) => updates(message as HasKeep));
   $pb.BuilderInfo get info_ => _i;
-  static HasKeep create() => new HasKeep();
+  @$core.pragma('dart2js:noInline')
+  static HasKeep create() => HasKeep._();
   HasKeep createEmptyInstance() => create();
-  static $pb.PbList<HasKeep> createRepeated() => new $pb.PbList<HasKeep>();
-  static HasKeep getDefault() => _defaultInstance ??= create()..freeze();
+  static $pb.PbList<HasKeep> createRepeated() => $pb.PbList<HasKeep>();
+  @$core.pragma('dart2js:noInline')
+  static HasKeep getDefault() =>
+      _defaultInstance ??= $pb.GeneratedMessage.$_defaultFor<HasKeep>(create);
   static HasKeep _defaultInstance;
 
-  int get aDrop => $_get(0, 0);
-  set aDrop(int v) {
+  @$pb.TagNumber(1)
+  $core.int get aDrop => $_getIZ(0);
+  @$pb.TagNumber(1)
+  set aDrop($core.int v) {
     $_setSignedInt32(0, v);
   }
 
-  bool hasADrop() => $_has(0);
+  @$pb.TagNumber(1)
+  $core.bool hasADrop() => $_has(0);
+  @$pb.TagNumber(1)
   void clearADrop() => clearField(1);
 }
 
 class ClearKeep extends $pb.GeneratedMessage {
-  static final $pb.BuilderInfo _i = new $pb.BuilderInfo('ClearKeep')
-    ..a<int>(1, 'aDrop', $pb.PbFieldType.O3)
-    ..hasRequiredFields = false;
+  static final $pb.BuilderInfo _i =
+      $pb.BuilderInfo('ClearKeep', createEmptyInstance: create)
+        ..a<$core.int>(1, 'aDrop', $pb.PbFieldType.O3, protoName: 'aDrop')
+        ..hasRequiredFields = false;
 
-  ClearKeep() : super();
-  ClearKeep.fromBuffer(List<int> i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromBuffer(i, r);
-  ClearKeep.fromJson(String i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromJson(i, r);
-  ClearKeep clone() => new ClearKeep()..mergeFromMessage(this);
+  ClearKeep._() : super();
+  factory ClearKeep() => create();
+  factory ClearKeep.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory ClearKeep.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  ClearKeep clone() => ClearKeep()..mergeFromMessage(this);
   ClearKeep copyWith(void Function(ClearKeep) updates) =>
       super.copyWith((message) => updates(message as ClearKeep));
   $pb.BuilderInfo get info_ => _i;
-  static ClearKeep create() => new ClearKeep();
+  @$core.pragma('dart2js:noInline')
+  static ClearKeep create() => ClearKeep._();
   ClearKeep createEmptyInstance() => create();
-  static $pb.PbList<ClearKeep> createRepeated() => new $pb.PbList<ClearKeep>();
-  static ClearKeep getDefault() => _defaultInstance ??= create()..freeze();
+  static $pb.PbList<ClearKeep> createRepeated() => $pb.PbList<ClearKeep>();
+  @$core.pragma('dart2js:noInline')
+  static ClearKeep getDefault() =>
+      _defaultInstance ??= $pb.GeneratedMessage.$_defaultFor<ClearKeep>(create);
   static ClearKeep _defaultInstance;
 
-  int get aDrop => $_get(0, 0);
-  set aDrop(int v) {
+  @$pb.TagNumber(1)
+  $core.int get aDrop => $_getIZ(0);
+  @$pb.TagNumber(1)
+  set aDrop($core.int v) {
     $_setSignedInt32(0, v);
   }
 
-  bool hasADrop() => $_has(0);
+  @$pb.TagNumber(1)
+  $core.bool hasADrop() => $_has(0);
+  @$pb.TagNumber(1)
   void clearADrop() => clearField(1);
 }
 
 class ZopDrop extends $pb.GeneratedMessage {
-  static final $pb.BuilderInfo _i = new $pb.BuilderInfo('ZopDrop')
-    ..a<int>(1, 'aDrop', $pb.PbFieldType.O3)
-    ..hasRequiredFields = false;
+  static final $pb.BuilderInfo _i =
+      $pb.BuilderInfo('ZopDrop', createEmptyInstance: create)
+        ..a<$core.int>(1, 'aDrop', $pb.PbFieldType.O3, protoName: 'aDrop')
+        ..hasRequiredFields = false;
 
-  ZopDrop() : super();
-  ZopDrop.fromBuffer(List<int> i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromBuffer(i, r);
-  ZopDrop.fromJson(String i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromJson(i, r);
-  ZopDrop clone() => new ZopDrop()..mergeFromMessage(this);
+  ZopDrop._() : super();
+  factory ZopDrop() => create();
+  factory ZopDrop.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory ZopDrop.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  ZopDrop clone() => ZopDrop()..mergeFromMessage(this);
   ZopDrop copyWith(void Function(ZopDrop) updates) =>
       super.copyWith((message) => updates(message as ZopDrop));
   $pb.BuilderInfo get info_ => _i;
-  static ZopDrop create() => new ZopDrop();
+  @$core.pragma('dart2js:noInline')
+  static ZopDrop create() => ZopDrop._();
   ZopDrop createEmptyInstance() => create();
-  static $pb.PbList<ZopDrop> createRepeated() => new $pb.PbList<ZopDrop>();
-  static ZopDrop getDefault() => _defaultInstance ??= create()..freeze();
+  static $pb.PbList<ZopDrop> createRepeated() => $pb.PbList<ZopDrop>();
+  @$core.pragma('dart2js:noInline')
+  static ZopDrop getDefault() =>
+      _defaultInstance ??= $pb.GeneratedMessage.$_defaultFor<ZopDrop>(create);
   static ZopDrop _defaultInstance;
 
-  int get aDrop => $_get(0, 0);
-  set aDrop(int v) {
+  @$pb.TagNumber(1)
+  $core.int get aDrop => $_getIZ(0);
+  @$pb.TagNumber(1)
+  set aDrop($core.int v) {
     $_setSignedInt32(0, v);
   }
 
-  bool hasADrop() => $_has(0);
+  @$pb.TagNumber(1)
+  $core.bool hasADrop() => $_has(0);
+  @$pb.TagNumber(1)
   void clearADrop() => clearField(1);
 }
 
 class MobDrop extends $pb.GeneratedMessage {
-  static final $pb.BuilderInfo _i = new $pb.BuilderInfo('MobDrop')
-    ..a<int>(1, 'aDrop', $pb.PbFieldType.O3)
-    ..hasRequiredFields = false;
+  static final $pb.BuilderInfo _i =
+      $pb.BuilderInfo('MobDrop', createEmptyInstance: create)
+        ..a<$core.int>(1, 'aDrop', $pb.PbFieldType.O3, protoName: 'aDrop')
+        ..hasRequiredFields = false;
 
-  MobDrop() : super();
-  MobDrop.fromBuffer(List<int> i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromBuffer(i, r);
-  MobDrop.fromJson(String i,
-      [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY])
-      : super.fromJson(i, r);
-  MobDrop clone() => new MobDrop()..mergeFromMessage(this);
+  MobDrop._() : super();
+  factory MobDrop() => create();
+  factory MobDrop.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory MobDrop.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  MobDrop clone() => MobDrop()..mergeFromMessage(this);
   MobDrop copyWith(void Function(MobDrop) updates) =>
       super.copyWith((message) => updates(message as MobDrop));
   $pb.BuilderInfo get info_ => _i;
-  static MobDrop create() => new MobDrop();
+  @$core.pragma('dart2js:noInline')
+  static MobDrop create() => MobDrop._();
   MobDrop createEmptyInstance() => create();
-  static $pb.PbList<MobDrop> createRepeated() => new $pb.PbList<MobDrop>();
-  static MobDrop getDefault() => _defaultInstance ??= create()..freeze();
+  static $pb.PbList<MobDrop> createRepeated() => $pb.PbList<MobDrop>();
+  @$core.pragma('dart2js:noInline')
+  static MobDrop getDefault() =>
+      _defaultInstance ??= $pb.GeneratedMessage.$_defaultFor<MobDrop>(create);
   static MobDrop _defaultInstance;
 
-  int get aDrop => $_get(0, 0);
-  set aDrop(int v) {
+  @$pb.TagNumber(1)
+  $core.int get aDrop => $_getIZ(0);
+  @$pb.TagNumber(1)
+  set aDrop($core.int v) {
     $_setSignedInt32(0, v);
   }
 
-  bool hasADrop() => $_has(0);
+  @$pb.TagNumber(1)
+  $core.bool hasADrop() => $_has(0);
+  @$pb.TagNumber(1)
   void clearADrop() => clearField(1);
 }
diff --git a/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/lib/generated/name_mangling.pb.dart b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/lib/generated/name_mangling.pb.dart
new file mode 100644
index 00000000000..bc76b278381
--- /dev/null
+++ b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/lib/generated/name_mangling.pb.dart
@@ -0,0 +1,80 @@
+///
+//  Generated code. Do not modify.
+//  source: name_mangling.proto
+//
+// @dart = 2.3
+// ignore_for_file: camel_case_types,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type
+
+import 'dart:core' as $core;
+
+import 'package:protobuf/protobuf.dart' as $pb;
+
+class AKeep extends $pb.GeneratedMessage {
+  static final $pb.BuilderInfo _i =
+      $pb.BuilderInfo('AKeep', createEmptyInstance: create)
+        ..hasRequiredFields = false;
+
+  AKeep._() : super();
+  factory AKeep() => create();
+  factory AKeep.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory AKeep.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  AKeep clone() => AKeep()..mergeFromMessage(this);
+  AKeep copyWith(void Function(AKeep) updates) =>
+      super.copyWith((message) => updates(message as AKeep));
+  $pb.BuilderInfo get info_ => _i;
+  @$core.pragma('dart2js:noInline')
+  static AKeep create() => AKeep._();
+  AKeep createEmptyInstance() => create();
+  static $pb.PbList<AKeep> createRepeated() => $pb.PbList<AKeep>();
+  @$core.pragma('dart2js:noInline')
+  static AKeep getDefault() =>
+      _defaultInstance ??= $pb.GeneratedMessage.$_defaultFor<AKeep>(create);
+  static AKeep _defaultInstance;
+}
+
+class NameManglingKeep extends $pb.GeneratedMessage {
+  static final $pb.BuilderInfo _i =
+      $pb.BuilderInfo('NameManglingKeep', createEmptyInstance: create)
+        ..aOM<AKeep>(10, 'clone', subBuilder: AKeep.create)
+        ..hasRequiredFields = false;
+
+  NameManglingKeep._() : super();
+  factory NameManglingKeep() => create();
+  factory NameManglingKeep.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory NameManglingKeep.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  NameManglingKeep clone() => NameManglingKeep()..mergeFromMessage(this);
+  NameManglingKeep copyWith(void Function(NameManglingKeep) updates) =>
+      super.copyWith((message) => updates(message as NameManglingKeep));
+  $pb.BuilderInfo get info_ => _i;
+  @$core.pragma('dart2js:noInline')
+  static NameManglingKeep create() => NameManglingKeep._();
+  NameManglingKeep createEmptyInstance() => create();
+  static $pb.PbList<NameManglingKeep> createRepeated() =>
+      $pb.PbList<NameManglingKeep>();
+  @$core.pragma('dart2js:noInline')
+  static NameManglingKeep getDefault() => _defaultInstance ??=
+      $pb.GeneratedMessage.$_defaultFor<NameManglingKeep>(create);
+  static NameManglingKeep _defaultInstance;
+
+  @$pb.TagNumber(10)
+  AKeep get clone_10 => $_getN(0);
+  @$pb.TagNumber(10)
+  set clone_10(AKeep v) {
+    setField(10, v);
+  }
+
+  @$pb.TagNumber(10)
+  $core.bool hasClone_10() => $_has(0);
+  @$pb.TagNumber(10)
+  void clearClone_10() => clearField(10);
+  @$pb.TagNumber(10)
+  AKeep ensureClone_10() => $_ensure(0);
+}
diff --git a/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/lib/name_mangling_test.dart b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/lib/name_mangling_test.dart
new file mode 100644
index 00000000000..b52c5dcdaca
--- /dev/null
+++ b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/lib/name_mangling_test.dart
@@ -0,0 +1,14 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:test/test.dart';
+
+import 'generated/name_mangling.pb.dart';
+
+main() {
+  NameManglingKeep n = NameManglingKeep.fromBuffer([]);
+  if (n.hasClone_10()) {
+    print("Has clone field");
+  }
+}
diff --git a/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/protos/foo.proto b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/protos/foo.proto
index 0a144338284..1f1087249aa 100644
--- a/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/protos/foo.proto
+++ b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/protos/foo.proto
@@ -34,8 +34,3 @@ message ZopDrop {
 message MobDrop {
   int32 aDrop = 1;
 }
-
-message A {
-  B unused = 1;
-  C used = 2;
-}
\ No newline at end of file
diff --git a/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/protos/name_mangling.proto b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/protos/name_mangling.proto
new file mode 100644
index 00000000000..f25b2f48fd2
--- /dev/null
+++ b/pkg/vm/testcases/transformations/protobuf_aware_treeshaker/protos/name_mangling.proto
@@ -0,0 +1,10 @@
+syntax = "proto3";
+
+message AKeep {}
+
+message NameManglingKeep {
+  // the name `clone` is mangled by the protoc_plugin to not conflict with
+  // `GeneratedMessage.clone`.
+  // Still we should be able to detect usages of this field.
+  AKeep clone = 10;
+}
\ No newline at end of file