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

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

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js;
 
 /**
  * The [ConstantHandler] keeps track of compile-time constants,
  * initializations of global and static fields, and default values of
  * optional parameters.
@@ skipping 31 matching lines @@
 
   String get name => 'ConstantHandler';
 
   void registerCompileTimeConstant(Constant constant) {
     registerInstantiatedClass(constant.computeType(compiler).element);
     if (constant.isFunction()) {
       FunctionConstant function = constant;
       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);
   }
 
   void registerInstantiatedClass(ClassElement element) {
     if (isMetadata) return;
     compiler.enqueuer.codegen.registerInstantiatedClass(element);
   }
 
   void registerStaticUse(Element element) {
@@ skipping 822 matching lines @@
             // Use the default value.
             fieldValue = handler.compileConstant(field);
           }
           jsNewArguments.add(fieldValue);
         },
         includeBackendMembers: true,
         includeSuperMembers: true);
     return jsNewArguments;
   }
 }