dart2js: compile metadata lazily in the lazy emitter.

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

Index: pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart b/pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart
index 78e6886205e491fe72aba767c166592d1324f879..aeeddc3afb936ee0a358f463cc47d5613669c1a3 100644
--- a/pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart
@@ -171,9 +171,7 @@ class Emitter implements emitterTask.Emitter {
         return js.js.expressionTemplateFor("('$isPrefix' + #) in #.prototype");
 
       case JsBuiltin.getMetadata:
-        String metadataAccess =
-            _emitter.generateEmbeddedGlobalAccessString(METADATA);
-        return js.js.expressionTemplateFor("$metadataAccess[#]");
+        return _emitter.templateForReadMetadata;
 
       case JsBuiltin.getType:
         return _emitter.templateForReadType;