Make RenderPass::Id an isolated class

cc/layers/render_surface_impl.h

Index: cc/layers/render_surface_impl.h
diff --git a/cc/layers/render_surface_impl.h b/cc/layers/render_surface_impl.h
index 27da8405699af1d7e5676816ca292ed22bc44b5e..52e4f386247aee0aa5f532ef2f9e419ac17c6c4a 100644
--- a/cc/layers/render_surface_impl.h
+++ b/cc/layers/render_surface_impl.h
@@ -24,6 +24,7 @@ class DamageTracker;
 class DelegatedRendererLayerImpl;
 template <typename LayerType>
 class OcclusionTracker;
+class RenderPassId;
 class RenderPassSink;
 class LayerImpl;
 template <typename LayerType>
@@ -131,14 +132,14 @@ class CC_EXPORT RenderSurfaceImpl {
 
   DamageTracker* damage_tracker() const { return damage_tracker_.get(); }
 
-  RenderPass::Id RenderPassId();
+  RenderPassId GetRenderPassId();
 
   void AppendRenderPasses(RenderPassSink* pass_sink);
   void AppendQuads(RenderPass* render_pass,
                    const OcclusionTracker<LayerImpl>& occlusion_tracker,
                    AppendQuadsData* append_quads_data,
                    bool for_replica,
-                   RenderPass::Id render_pass_id);
+                   RenderPassId render_pass_id);
 
  private:
   LayerImpl* owning_layer_;