compositor-worker: cc->blink mutation plumbing

cc/trees/proxy_main.cc

 // Copyright 2015 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.
 
 #include "cc/trees/proxy_main.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/trace_event/trace_event.h"
@@ skipping 166 matching lines @@
     TRACE_EVENT_INSTANT0("cc", "EarlyOut_OutputSurfaceLost",
                          TRACE_EVENT_SCOPE_THREAD);
     channel_main_->BeginMainFrameAbortedOnImpl(
         CommitEarlyOutReason::ABORTED_OUTPUT_SURFACE_LOST,
         begin_main_frame_start_time);
     return;
   }
 
   current_pipeline_stage_ = ANIMATE_PIPELINE_STAGE;
 
+  if (begin_main_frame_state->begin_frame_callbacks) {
+    for (auto& callback : *begin_main_frame_state->begin_frame_callbacks)
+      callback.Run();
+  }
+
   layer_tree_host_->ApplyScrollAndScale(
       begin_main_frame_state->scroll_info.get());
 
   layer_tree_host_->WillBeginMainFrame();
 
   layer_tree_host_->BeginMainFrame(begin_main_frame_state->begin_frame_args);
   layer_tree_host_->AnimateLayers(
       begin_main_frame_state->begin_frame_args.frame_time);
 
   // Recreate all UI resources if there were evicted UI resources when the impl
@@ skipping 269 matching lines @@
     return false;
   channel_main_->SetNeedsCommitOnImpl();
   return true;
 }
 
 bool ProxyMain::IsMainThread() const {
   return task_runner_provider_->IsMainThread();
 }
 
 }  // namespace cc