Make RenderPass::Id an isolated class

cc/test/render_pass_test_common.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_TEST_RENDER_PASS_TEST_COMMON_H_
 #define CC_TEST_RENDER_PASS_TEST_COMMON_H_
 
 #include "cc/quads/render_pass.h"
 
 namespace cc {
 class ResourceProvider;
 }
 
 namespace cc {
 
 class TestRenderPass : public RenderPass {
  public:
   static scoped_ptr<TestRenderPass> Create() {
     return make_scoped_ptr(new TestRenderPass);
   }
 
   static const unsigned int kSyncPointForMailboxTextureQuad = 30;
 
   void AppendOneOfEveryQuadType(ResourceProvider* resource_provider,
-                                RenderPass::Id child_pass);
+                                RenderPassId child_pass);
 
  protected:
   TestRenderPass() : RenderPass() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_RENDER_PASS_TEST_COMMON_H_