Update from https://crrev.com/312398

cc/debug/frame_timing_tracker.h

+// 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.
+
+#ifndef CC_DEBUG_FRAME_TIMING_TRACKER_H_
+#define CC_DEBUG_FRAME_TIMING_TRACKER_H_
+
+#include <utility>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/containers/hash_tables.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
+#include "cc/base/cc_export.h"
+
+namespace cc {
+
+// This class maintains a history of timestamps and rect IDs to communicate
+// frame events back to Blink
+// TODO(mpb): Start using this. crbug.com/442554
+class CC_EXPORT FrameTimingTracker {
+ public:
+  struct CC_EXPORT CompositeTimingEvent {
+    CompositeTimingEvent(int, base::TimeTicks);
+    ~CompositeTimingEvent();
+
+    int frame_id;
+    base::TimeTicks timestamp;
+  };
+
+  using CompositeTimingSet =
+      base::hash_map<int, std::vector<CompositeTimingEvent>>;
+
+  static scoped_ptr<FrameTimingTracker> Create();
+
+  ~FrameTimingTracker();
+
+  // This routine takes all of the individual CompositeEvents stored in the
+  // tracker and collects them by "rect_id", as in the example below.
+  // [ {f_id1,r_id1,t1}, {f_id2,r_id1,t2}, {f_id3,r_id2,t3} ]
+  // ====>
+  // [ {r_id1,<{f_id1,t1},{f_id2,t2}>}, {r_id2,<{f_id3,t3}>} ]
+  scoped_ptr<CompositeTimingSet> GroupCountsByRectId();
+
+  // This routine takes a timestamp and an array of frame_id,rect_id pairs
+  // and generates CompositeTimingEvents (frame_id, timestamp) and adds them to
+  // internal hash_map keyed on rect_id
+  using FrameAndRectIds = std::pair<int, int64_t>;
+  void SaveTimeStamps(base::TimeTicks timestamp,
+                      const std::vector<FrameAndRectIds>& frame_ids);
+
+ private:
+  FrameTimingTracker();
+
+  scoped_ptr<CompositeTimingSet> composite_events_;
+
+  DISALLOW_COPY_AND_ASSIGN(FrameTimingTracker);
+};
+
+}  // namespace cc
+
+#endif  // CC_DEBUG_FRAME_TIMING_TRACKER_H_