dart2js: Implement frequency based naming.

pkg/compiler/lib/src/js_backend/js_backend.dart

Index: pkg/compiler/lib/src/js_backend/js_backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/js_backend.dart b/pkg/compiler/lib/src/js_backend/js_backend.dart
index f36157109d6d8cb688b6b52747600c61c9a6d32a..a653e314a92c399bd80bae497202af8fb7c2cfc3 100644
--- a/pkg/compiler/lib/src/js_backend/js_backend.dart
+++ b/pkg/compiler/lib/src/js_backend/js_backend.dart
@@ -25,12 +25,8 @@ import '../io/source_information.dart' show SourceInformationFactory;
 import '../js/js.dart' as jsAst;
 import '../js/js.dart' show js;
 import '../js_emitter/js_emitter.dart'
-    show Emitter,
-         CodeEmitterTask,
-         ClassBuilder,
-         MetadataCollector,
-         Placeholder,
-         USE_NEW_EMITTER;
+    show ClassBuilder, CodeEmitterTask, Emitter, MetadataCollector, Placeholder,
+        TokenFinalizer, USE_NEW_EMITTER;
 
 import '../library_loader.dart' show LibraryLoader, LoadedLibraries;
 import '../native/native.dart' as native;
@@ -55,9 +51,11 @@ part 'checked_mode_helpers.dart';
 part 'constant_emitter.dart';
 part 'constant_handler_javascript.dart';
 part 'custom_elements_analysis.dart';
+part 'frequency_namer.dart';
 part 'field_naming_mixin.dart';
 part 'minify_namer.dart';
 part 'namer.dart';
+part 'namer_names.dart';
 part 'no_such_method_registry.dart';
 part 'runtime_types.dart';
 part 'type_variable_handler.dart';