Handle @proxy classes in type checker.

sdk/lib/_internal/compiler/implementation/compiler.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;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 422 matching lines @@
   ClassElement stringClass;
   ClassElement functionClass;
   ClassElement nullClass;
   ClassElement listClass;
   ClassElement typeClass;
   ClassElement mapClass;
   ClassElement symbolClass;
   ClassElement stackTraceClass;
   ClassElement typedDataClass;
 
+  /// The constant for the [proxy] variable defined in dart:core.
+  Constant proxyConstant;
+
   // Initialized after symbolClass has been resolved.
   FunctionElement symbolConstructor;
 
   // Initialized when dart:mirrors is loaded.
   ClassElement mirrorSystemClass;
 
   // Initialized when dart:mirrors is loaded.
   ClassElement mirrorsUsedClass;
 
   // Initialized after mirrorSystemClass has been resolved.
@@ skipping 456 matching lines @@
           'dart:_js_helper library does not contain required classes: '
           '$missingHelperClasses');
     }
 
     if (types == null) {
       types = new Types(this, dynamicClass);
     }
     backend.initializeHelperClasses();
 
     dynamicClass.ensureResolved(this);
+
+    proxyConstant = constantHandler.compileVariable(
+        coreLibrary.find('proxy'), isConst: true);
   }
 
   Element _unnamedListConstructor;
   Element get unnamedListConstructor {
     if (_unnamedListConstructor != null) return _unnamedListConstructor;
     Selector callConstructor = new Selector.callConstructor(
         "", listClass.getLibrary());
     return _unnamedListConstructor =
         listClass.lookupConstructor(callConstructor);
   }
@@ skipping 743 matching lines @@
 
   void close() {}
 
   toString() => name;
 
   /// Convenience method for getting an [api.CompilerOutputProvider].
   static NullSink outputProvider(String name, String extension) {
     return new NullSink('$name.$extension');
   }
 }