Add IPC messages to transfer compositor protos

content/public/browser/web_contents_delegate.h

Index: content/public/browser/web_contents_delegate.h
diff --git a/content/public/browser/web_contents_delegate.h b/content/public/browser/web_contents_delegate.h
index 40a49049a8511d9aa9f95cb6b8a0007ac3d38a9c..f6a04a5c40ff310206abf9336b81b88173cca69c 100644
--- a/content/public/browser/web_contents_delegate.h
+++ b/content/public/browser/web_contents_delegate.h
@@ -510,6 +510,10 @@ class CONTENT_EXPORT WebContentsDelegate {
       WebContents* web_contents,
       int cert_id);
 
+  // Called when the active render widget is forwarding a RemoteChannel
+  // compositor proto.  This is used in Blimp mode.
+  virtual void ForwardCompositorProto(const std::vector<uint8_t>& proto) {}
+
  protected:
   virtual ~WebContentsDelegate();