dart2js: is-checks for the new emitter.

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

Index: pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart b/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
index 40a747308c37b9f4be70cc4cc5ec6662b73d3d74..0ee0dbaa89160abf8919c3358c150b896040fb00 100644
--- a/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
@@ -137,6 +137,7 @@ class OldEmitter implements Emitter {
     buffer.write(jsAst.prettyPrint(js.comment(comment), compiler));
   }
 
+  @override
   jsAst.Expression constantReference(ConstantValue value) {
     return constantEmitter.reference(value);
   }
@@ -178,6 +179,7 @@ class OldEmitter implements Emitter {
   /// All the global state can be passed around with this variable.
   String get globalsHolder => namer.getMappedGlobalName("globalsHolder");
 
+  @override
   jsAst.Expression generateEmbeddedGlobalAccess(String global) {
     return js(generateEmbeddedGlobalAccessString(global));
   }
@@ -187,38 +189,55 @@ class OldEmitter implements Emitter {
     return '$initName.$global';
   }
 
-  jsAst.Expression isolateLazyInitializerAccess(Element element) {
+  jsAst.PropertyAccess globalPropertyAccess(Element element) {
+    String name = namer.getNameX(element);
+    jsAst.PropertyAccess pa = new jsAst.PropertyAccess.field(
+        new jsAst.VariableUse(namer.globalObjectFor(element)),
+        name);
+    return pa;
+  }
+
+  @override
+  jsAst.Expression isolateLazyInitializerAccess(FieldElement element) {
      return jsAst.js('#.#', [namer.globalObjectFor(element),
                              namer.getLazyInitializerName(element)]);
    }
 
-  jsAst.Expression isolateStaticClosureAccess(Element element) {
+  @override
+  jsAst.Expression isolateStaticClosureAccess(FunctionElement element) {
      return jsAst.js('#.#()',
          [namer.globalObjectFor(element), namer.getStaticClosureName(element)]);
    }
 
-  jsAst.PropertyAccess globalPropertyAccess(Element element) {
-    String name = namer.getNameX(element);
-    jsAst.PropertyAccess pa = new jsAst.PropertyAccess.field(
-        new jsAst.VariableUse(namer.globalObjectFor(element)),
-        name);
-    return pa;
+  @override
+  jsAst.PropertyAccess staticFieldAccess(FieldElement element) {
+    return globalPropertyAccess(element);
+  }
+
+  @override
+  jsAst.PropertyAccess staticFunctionAccess(FunctionElement element) {
+    return globalPropertyAccess(element);
   }
 
-  jsAst.PropertyAccess staticFieldAccess(Element element) {
-      return globalPropertyAccess(element);
+  @override
+  jsAst.PropertyAccess constructorAccess(ClassElement element) {
+    return globalPropertyAccess(element);
   }
 
-  jsAst.PropertyAccess staticFunctionAccess(Element element) {
-      return globalPropertyAccess(element);
+  @override
+  jsAst.PropertyAccess prototypeAccess(ClassElement element,
+                                       bool hasBeenInstantiated) {
+    return jsAst.js('#.prototype', constructorAccess(element));
   }
 
-  jsAst.PropertyAccess classAccess(Element element) {
-        return globalPropertyAccess(element);
+  @override
+  jsAst.PropertyAccess interceptorClassAccess(ClassElement element) {
+    return globalPropertyAccess(element);
   }
 
-  jsAst.PropertyAccess typedefAccess(Element element) {
-       return globalPropertyAccess(element);
+  @override
+  jsAst.PropertyAccess typeAccess(Element element) {
+    return globalPropertyAccess(element);
   }
 
   jsAst.FunctionDeclaration get generateAccessorFunction {