Report LatencyInfo through trace buffer

ui/events/gestures/gesture_sequence.cc

 // 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.
 
 #include "ui/events/gestures/gesture_sequence.h"
 
 #include <stdlib.h>
 #include <cmath>
 
 #include "base/command_line.h"
@@ skipping 578 matching lines @@
     point.Reset();
     --point_count_;
     CHECK_GE(point_count_, 0);
     RecreateBoundingBox();
     if (state_ == GS_PINCH) {
       pinch_distance_current_ = BoundingBoxDiagonal(bounding_box_);
       pinch_distance_start_ = pinch_distance_current_;
     }
   }
 
-  const ui::LatencyInfo* touch_latency = event.latency();
-  Gestures::iterator it = gestures->begin();
-  for (; it != gestures->end(); it++) {
-    (*it)->latency()->MergeWith(*touch_latency);
+  // If the touch event does not cause any rendering scheduled, then
+  // 1) If the touch event does not generate any gesture event, its
+  //    LatencyInfo ends here.
+  // 2) If the touch event generates gesture events, its latencyinfo
+  //    is copied into the gesture events.
+  if (!event.latency()->FindLatency(
+          ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT, 0, NULL)) {
+    if (gestures->empty()) {
+      ui::LatencyInfo* touch_latency =
+          const_cast<ui::LatencyInfo*>(event.latency());
+      touch_latency->AddLatencyNumber(
+          ui::INPUT_EVENT_LATENCY_TERMINATED_TOUCH_COMPONENT, 0, 0);
+    } else {
+      Gestures::iterator it = gestures->begin();
+      for (; it != gestures->end(); it++) {
+        (*it)->latency()->MergeWith(*event.latency());
+        // Inheriting the trace_id from the touch event's LatencyInfo
+        (*it)->latency()->trace_id = event.latency()->trace_id;
+      }
+    }

[sadrul, 2013/10/09 19:23:27]

Please move this block of code into a separate independent function (e.g.
UpdateGestureEventLatencyInfo). This code should probably live elsewhere, since
the GR seems like an odd place for this. Moving to a separate function will
allow to move this out when there's a better place for this.

[Yufeng Shen (Slow to review), 2013/10/09 20:53:50]

Done.

   }
 
   return gestures.release();
 }
 
 void GestureSequence::RecreateBoundingBox() {
   // TODO(sad): Recreating the bounding box at every touch-event is not very
   // efficient. This should be made better.
   if (point_count_ == 0) {
     bounding_box_.SetRect(0, 0, 0, 0);
@@ skipping 616 matching lines @@
     return;
 
   // Since long press timer has been started, there should be a non-NULL point.
   const GesturePoint* point = GetPointByPointId(0);
   if (!ui::gestures::IsInsideManhattanSquare(point->first_touch_position(),
       event.location()))
     GetLongPressTimer()->Stop();
 }
 
 }  // namespace ui