Test that main thread frames cease to fire during composited animation

cc/output/compositor_frame_metadata.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_OUTPUT_COMPOSITOR_FRAME_METADATA_H_
 #define CC_OUTPUT_COMPOSITOR_FRAME_METADATA_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 79 matching lines @@
   uint32_t content_source_id = 0;
 
   // BeginFrameAck for the BeginFrame that this CompositorFrame answers.
   BeginFrameAck begin_frame_ack;
 
   // Once the display compositor processes a frame containing a non-zero frame
   // token, the token is sent to embedder of the frame. This is helpful when
   // the embedder wants to do something after a particular frame is processed.
   uint32_t frame_token = 0;
 
+  bool is_main_thread_frame = true;
+
  private:
   CompositorFrameMetadata(const CompositorFrameMetadata& other);
   CompositorFrameMetadata operator=(const CompositorFrameMetadata&) = delete;
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_COMPOSITOR_FRAME_METADATA_H_