Support encoding of NaN, infinity and negative infinity.

BUG=
R=sigmund@google.com

Review URL: https://codereview.chromium.org/2250643002 .

pkg/compiler/lib/src/serialization/json_serializer.dart

@@ -15,8 +15,13 @@ class JsonSerializationEncoder implements SerializationEncoder {
   const JsonSerializationEncoder();
 
   String encode(ObjectValue objectValue) {
-    return new JsonEncoder.withIndent(' ')
-        .convert(const JsonValueEncoder().convert(objectValue));
+    try {
+      return new JsonEncoder.withIndent(' ')
+          .convert(const JsonValueEncoder().convert(objectValue));
+    } on JsonUnsupportedObjectError catch (e) {
+      throw 'Error encoding `${e.unsupportedObject}` '
+          '(${e.unsupportedObject.runtimeType})';
+    }
   }
 }
 
@@ -48,7 +53,19 @@ class JsonValueEncoder implements ValueVisitor {
   visitConstant(ConstantValue value, arg) => visit(value.id);
 
   @override
-  double visitDouble(DoubleValue value, arg) => value.value;
+  visitDouble(DoubleValue value, arg) {
+    double d = value.value;
+    if (d.isNaN) {
+      return 'NaN';
+    } else if (d.isInfinite) {
+      if (d.isNegative) {
+        return '-Infinity';
+      } else {
+        return 'Infinity';
+      }
+    }
+    return d;
+  }
 
   @override
   visitElement(ElementValue value, arg) => visit(value.id);

pkg/compiler/lib/src/serialization/serialization.dart

@@ -540,13 +540,21 @@ abstract class AbstractDecoder<K> {
   /// If no value is associated with [key], then if [isOptional] is `true`,
   /// [defaultValue] is returned, otherwise an exception is thrown.
   double getDouble(K key, {bool isOptional: false, double defaultValue}) {
-    double value = _map[_getKeyValue(key)];
+    var value = _map[_getKeyValue(key)];
     if (value == null) {
       if (isOptional || defaultValue != null) {
         return defaultValue;
       }
       throw new StateError("double value '$key' not found in $_map.");
     }
+    // Support alternative encoding of NaN and +/- infinity for JSON.
+    if (value == 'NaN') {
+      return double.NAN;
+    } else if (value == '-Infinity') {
+      return double.NEGATIVE_INFINITY;
+    } else if (value == 'Infinity') {
+      return double.INFINITY;
+    }
     return value;
   }
 

tests/compiler/dart2js/serialization/test_data.dart

@@ -683,6 +683,14 @@ main() => y;
   }, preserializedSourceFiles: const {
     'a.dart': '''
 var x, y = 2;
+''',
+  }),
+
+  const Test('Double values', const {},
+      preserializedSourceFiles: const {
+  'main.dart': '''
+const a = 1e+400;
+main() => a;
 ''',
   }),
 ];