Trace main thread commit in flow events.

cc/trees/layer_tree_host.h

 // Copyright 2011 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_TREES_LAYER_TREE_HOST_H_
 #define CC_TREES_LAYER_TREE_HOST_H_
 
 #include <limits>
 #include <set>
 #include <string>
@@ skipping 293 matching lines @@
   void RemoveSwapPromiseMonitor(SwapPromiseMonitor* monitor);
 
   // Call this function when you expect there to be a swap buffer.
   // See swap_promise.h for how to use SwapPromise.
   void QueueSwapPromise(scoped_ptr<SwapPromise> swap_promise);
 
   void BreakSwapPromises(SwapPromise::DidNotSwapReason reason);
 
   size_t num_queued_swap_promises() const { return swap_promise_list_.size(); }
 
+  void trace_commit() {

[Yufeng Shen (Slow to review), 2015/06/16 15:11:05]

Can you use Camel style ? underscore style is usually only for simple
setter/getter. And probably move the implementation to .cc file.

Also a different name more specific to SwapPromise, maybe
OnCommitForSwapPromises()

+    for (unsigned int i = 0; i < num_queued_swap_promises(); i++) {
+      SwapPromise* swap_promise_ = swap_promise_list_.at(i);
+
+      swap_promise_->OnCommit();
+    }

[Yufeng Shen (Slow to review), 2015/06/16 15:11:05]

It can be simplified like this:

for (auto* swap_promise : swap_promise_list_)
    swap_promise->OnCommit()

+  }
+
   void set_surface_id_namespace(uint32_t id_namespace);
   SurfaceSequence CreateSurfaceSequence();
 
   void SetChildrenNeedBeginFrames(bool children_need_begin_frames) const;
   void SendBeginFramesToChildren(const BeginFrameArgs& args) const;
 
   void SetAuthoritativeVSyncInterval(const base::TimeDelta& interval);
 
   PropertyTrees* property_trees() { return &property_trees_; }
   bool needs_meta_info_recomputation() {
@@ skipping 165 matching lines @@
 
   uint32_t surface_id_namespace_;
   uint32_t next_surface_sequence_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_H_