dart2js: split out types from metadata.

pkg/compiler/lib/src/js_emitter/metadata_collector.dart

Index: pkg/compiler/lib/src/js_emitter/metadata_collector.dart
diff --git a/pkg/compiler/lib/src/js_emitter/metadata_collector.dart b/pkg/compiler/lib/src/js_emitter/metadata_collector.dart
index 5319a878eb1094083db8781e528fb2f3306f795f..9876dacd6ace666e315f5468244f61204c14c3fb 100644
--- a/pkg/compiler/lib/src/js_emitter/metadata_collector.dart
+++ b/pkg/compiler/lib/src/js_emitter/metadata_collector.dart
@@ -9,12 +9,19 @@ class MetadataCollector {
   final Emitter _emitter;
 
   /// A list of JS expressions that represent metadata, parameter names and
-  /// type, and return types.
-  final List<String> globalMetadata = [];
+  /// type variable types.
+  final List<String> globalMetadata = <String>[];
 
   /// A map used to canonicalize the entries of globalMetadata.
   final Map<String, int> _globalMetadataMap = <String, int>{};
 
+  /// A list of JS expression representing types including function types and
+  /// typedefs.
+  final List<String> types = <String>[];
+
+  /// A map used to canonicalize the entries of types.
+  final Map<String, int> _typesMap = <String, int>{};
+
   MetadataCollector(this._compiler, this._emitter);
 
   JavaScriptBackend get _backend => _compiler.backend;
@@ -96,7 +103,7 @@ class MetadataCollector {
               return _backend.isAccessibleByReflection(typedef.element);
             });
 
-    return addGlobalMetadata(
+    return addType(
         jsAst.prettyPrint(representation, _compiler).getText());
   }
 
@@ -111,6 +118,13 @@ class MetadataCollector {
     });
   }
 
+  int addType(String compiledType) {
+    return _typesMap.putIfAbsent(compiledType, () {
+      types.add(compiledType);
+      return types.length - 1;
+    });
+  }
+
   List<int> computeMetadata(FunctionElement element) {
     return _compiler.withCurrentElement(element, () {
       if (!_mustEmitMetadataFor(element)) return const <int>[];