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>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/cancelable_callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
+#include "base/trace_event/trace_event.h"
 #include "cc/animation/animation_events.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/scoped_ptr_vector.h"
 #include "cc/debug/frame_timing_tracker.h"
 #include "cc/debug/micro_benchmark.h"
 #include "cc/debug/micro_benchmark_controller.h"
 #include "cc/input/input_handler.h"
 #include "cc/input/layer_selection_bound.h"
 #include "cc/input/scrollbar.h"
 #include "cc/input/top_controls_state.h"
@@ skipping 273 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() {
+    for (unsigned int i = 0; i < num_queued_swap_promises(); i++) {
+      SwapPromise* swap_promise_ = swap_promise_list_.at(i);
+
+      TRACE_EVENT_FLOW_STEP0("input,benchmark", "LatencyInfo.Flow",
+                             TRACE_ID_DONT_MANGLE(swap_promise_->TraceId()),

[Yufeng Shen (Slow to review), 2015/06/15 23:48:25]

Not all SwapPromise is carrying LatencyInfo with it, so its TraceId()
can'be always interpreted as the trace_id for LatencyInfo.

I think you should have a
virtual SwapPromise::OnCommit() {}

and only in LatencyInfoSwapPromise::OnCommit()
you can use the trace_id for adding the flow event.

+                             "HanldeInputEventMainCommit");
+    }
+  }
+
   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_