dart2js: Use frequency of occurence to sort metadata indices.

pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart b/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
index 912fa4b2df6a70e08436a184d3d28df918e80877..61e206e991dbb59025f5116dc1537d9e1990b693 100644
--- a/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
@@ -138,8 +138,8 @@ class ModelEmitter {
     // deferred hash (which depends on the output) when emitting the main
     // fragment.
     fragments.skip(1).forEach((DeferredFragment deferredUnit) {
-      List<js.Expression> types =
-          program.metadataTypes[deferredUnit.outputUnit];
+      js.Expression types =
+          program.metadataTypesForOutputUnit(deferredUnit.outputUnit);
       js.Expression ast = emitDeferredFragment(types, deferredUnit,
                                                program.holders);
       String code = js.prettyPrint(ast, compiler).getText();
@@ -192,7 +192,6 @@ class ModelEmitter {
         emitLazilyInitializedStatics(fragment.staticLazilyInitializedFields));
     elements.add(emitConstants(fragment.constants));
 
-
     js.Expression code = new js.ArrayInitializer(elements);
 
     Map<String, dynamic> holes =
@@ -492,21 +491,19 @@ class ModelEmitter {
 
     List<js.Property> metadataGlobals = <js.Property>[];
 
-    js.ArrayInitializer unparsedMetadata = unparseExpressions(program.metadata);
-    metadataGlobals.add(new js.Property(js.string(lazyMetadataName),
-                                        unparsedMetadata));
-    metadataGlobals.add(new js.Property(js.string(METADATA),
-                                        new js.ArrayInitializer([])));
+    js.Property createGlobal(js.Expression metadata, String global) {
+      return new js.Property(js.string(global), metadata);
+    }
 
-    List<js.Expression> types =
-        program.metadataTypes[program.fragments.first.outputUnit];
-    metadataGlobals.add(new js.Property(js.string(TYPES),
-                                        unparseExpressions(types)));
+    metadataGlobals.add(createGlobal(program.metadata, METADATA));
+    js.Expression types =
+        program.metadataTypesForOutputUnit(program.mainFragment.outputUnit);
+    metadataGlobals.add(createGlobal(types, TYPES));
 
     return metadataGlobals;
   }
 
-  js.Expression emitDeferredFragment(List<js.Expression> types,
+  js.Expression emitDeferredFragment(js.Expression deferredTypes,
                                      DeferredFragment fragment,
                                      List<Holder> holders) {
     // TODO(floitsch): initialize eager classes.
@@ -531,10 +528,6 @@ class ModelEmitter {
 
     js.LiteralString immediateString = unparse(compiler, immediateCode);
 
-    js.Expression deferredTypes = (types == null)
-        ? js.string("[]")
-        : unparse(compiler, new js.ArrayInitializer(types));
-
     js.ArrayInitializer hunk =
         new js.ArrayInitializer([deferredArray, immediateString,
                                  deferredTypes]);