Reusing base::IdType<...> to implement SurfaceId.

content/renderer/child_frame_compositing_helper.h

Index: content/renderer/child_frame_compositing_helper.h
diff --git a/content/renderer/child_frame_compositing_helper.h b/content/renderer/child_frame_compositing_helper.h
index 1f26c9fffe8e0a914a14d8663f0be4856b0053f6..be540ea30bb24dadd9b3de9d59138848e7b3949a 100644
--- a/content/renderer/child_frame_compositing_helper.h
+++ b/content/renderer/child_frame_compositing_helper.h
@@ -12,6 +12,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/shared_memory.h"
 #include "cc/layers/delegated_frame_resource_collection.h"
+#include "cc/surfaces/surface_id.h"
 #include "content/common/content_export.h"
 #include "ui/gfx/geometry/size.h"
 
@@ -20,7 +21,6 @@ class SharedMemory;
 }
 
 namespace cc {
-struct SurfaceId;
 struct SurfaceSequence;
 
 class CompositorFrame;