Make RenderPass::Id an isolated class

cc/output/direct_renderer.h

Index: cc/output/direct_renderer.h
diff --git a/cc/output/direct_renderer.h b/cc/output/direct_renderer.h
index 442d371e26b8154734a8524b8577e74f8635a7ef..0911862c5b3547342b6290a923f7a8e727de6293 100644
--- a/cc/output/direct_renderer.h
+++ b/cc/output/direct_renderer.h
@@ -28,8 +28,7 @@ class CC_EXPORT DirectRenderer : public Renderer {
 
   virtual void DecideRenderPassAllocationsForFrame(
       const RenderPassList& render_passes_in_draw_order) OVERRIDE;
-  virtual bool HasAllocatedResourcesForTesting(RenderPass::Id id) const
-      OVERRIDE;
+  virtual bool HasAllocatedResourcesForTesting(RenderPassId id) const OVERRIDE;
   virtual void DrawFrame(RenderPassList* render_passes_in_draw_order,
                          float device_scale_factor,
                          const gfx::Rect& device_viewport_rect,
@@ -116,7 +115,7 @@ class CC_EXPORT DirectRenderer : public Renderer {
       DrawingFrame* frame,
       scoped_ptr<CopyOutputRequest> request) = 0;
 
-  base::ScopedPtrHashMap<RenderPass::Id, ScopedResource> render_pass_textures_;
+  base::ScopedPtrHashMap<RenderPassId, ScopedResource> render_pass_textures_;
   OutputSurface* output_surface_;
   ResourceProvider* resource_provider_;
   scoped_ptr<OverlayProcessor> overlay_processor_;