[kernel] add ability to disable offsets for bazel worker to use

This is a lightly modified version of Jennys CL @
https://dart-review.googlesource.com/100275

Change-Id: I46a1665d84d04602af1f338cf963bc25b4e6b25c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/101280
Commit-Queue: Jens Johansen <jensj@google.com>
Reviewed-by: Kevin Millikin <kmillikin@google.com>

pkg/front_end/lib/src/fasta/kernel/utils.dart

@@ -60,12 +60,15 @@ Future<Null> writeComponentToFile(Component component, Uri uri,
 
 /// Serialize the libraries in [component] that match [filter].
 List<int> serializeComponent(Component component,
-    {bool filter(Library library), bool includeSources: true}) {
+    {bool filter(Library library),
+    bool includeSources: true,
+    bool includeOffsets: true}) {
   ByteSink byteSink = new ByteSink();
   BinaryPrinter printer = filter == null
-      ? new BinaryPrinter(byteSink, includeSources: includeSources)
-      : new LimitedBinaryPrinter(
-          byteSink, filter ?? (_) => true, !includeSources);
+      ? new BinaryPrinter(byteSink,
+          includeSources: includeSources, includeOffsets: includeOffsets)
+      : new LimitedBinaryPrinter(byteSink, filter, !includeSources,
+          includeOffsets: includeOffsets);
   printer.writeComponentFile(component);
   return byteSink.builder.takeBytes();
 }

pkg/kernel/lib/binary/ast_to_binary.dart

@@ -37,6 +37,7 @@ class BinaryPrinter implements Visitor<void>, BinarySink {
   BufferedSink _constantsSink;
   BufferedSink _sink;
   bool includeSources;
+  bool includeOffsets;
 
   List<int> libraryOffsets;
   List<int> classOffsets;
@@ -57,7 +58,9 @@ class BinaryPrinter implements Visitor<void>, BinarySink {
   /// The BinaryPrinter will use its own buffer, so the [sink] does not need
   /// one.
   BinaryPrinter(Sink<List<int>> sink,
-      {StringIndexer stringIndexer, this.includeSources = true})
+      {StringIndexer stringIndexer,
+      this.includeSources = true,
+      this.includeOffsets = true})
       : _mainSink = new BufferedSink(sink),
         _metadataSink = new BufferedSink(new BytesSink()),
         _constantsBytesSink = new BytesSink(),
@@ -875,7 +878,11 @@ class BinaryPrinter implements Visitor<void>, BinarySink {
     // TODO(jensj): Delta-encoding.
     // File offset ranges from -1 and up,
     // but is here saved as unsigned (thus the +1)
-    writeUInt30(offset + 1);
+    if (!includeOffsets) {
+      writeUInt30(0);
+    } else {
+      writeUInt30(offset + 1);
+    }
   }
 
   void writeClassReference(Class class_) {

pkg/kernel/lib/binary/limited_ast_to_binary.dart

@@ -23,8 +23,11 @@ class LimitedBinaryPrinter extends BinaryPrinter {
   final bool excludeUriToSource;
 
   LimitedBinaryPrinter(
-      Sink<List<int>> sink, this.predicate, this.excludeUriToSource)
-      : super(sink, includeSources: !excludeUriToSource);
+      Sink<List<int>> sink, this.predicate, this.excludeUriToSource,
+      {bool includeOffsets = true})
+      : super(sink,
+            includeSources: !excludeUriToSource,
+            includeOffsets: includeOffsets);
 
   @override
   void computeCanonicalNames(Component component) {

utils/bazel/kernel_worker.dart

@@ -291,6 +291,8 @@ Future<ComputeKernelResult> computeKernel(List<String> args,
         incrementalComponent.problemsAsJson = null;
         incrementalComponent.mainMethod = null;
         target.performOutlineTransformations(incrementalComponent);
+        return Future.value(fe.serializeComponent(incrementalComponent,
+            includeSources: false, includeOffsets: false));
       }
 
       return Future.value(fe.serializeComponent(incrementalComponent));