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

content/renderer/render_frame_proxy.h

Index: content/renderer/render_frame_proxy.h
diff --git a/content/renderer/render_frame_proxy.h b/content/renderer/render_frame_proxy.h
index f6dc70054cf17d0771f7778e82da3a2daa783bea..a6cd6350e1bdac213a7ccd0622f98b428df0d7db 100644
--- a/content/renderer/render_frame_proxy.h
+++ b/content/renderer/render_frame_proxy.h
@@ -7,6 +7,7 @@
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "cc/surfaces/surface_id.h"
 #include "content/common/content_export.h"
 #include "ipc/ipc_listener.h"
 #include "ipc/ipc_sender.h"
@@ -24,7 +25,6 @@ struct WebRect;
 }
 
 namespace cc {
-struct SurfaceId;
 struct SurfaceSequence;
 }