Fix warnings in dart2js code and re-enable analyzer coverage.

sdk/lib/_internal/compiler/implementation/compile_time_constants.dart

Index: sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart b/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
index a4153158d95bb482906a0c3d445caaaa36727d8e..a532fe0136d9de9a842dfd3b2bb3f1afe9629a68 100644
--- a/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
+++ b/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
@@ -49,7 +49,8 @@ class ConstantHandler extends CompilerTask {
       registerGetOfStaticFunction(function.element);
     } else if (constant.isInterceptor()) {
       // An interceptor constant references the class's prototype chain.
-      registerInstantiatedClass(constant.dispatchedType.element);
+      InterceptorConstant interceptor = constant;
+      registerInstantiatedClass(interceptor.dispatchedType.element);
     }
     compiledConstants.add(constant);
   }