Pass ui::LatencyInfo correct with unified gesture detector on Aura.

ui/events/gestures/gesture_provider_aura.cc

 // Copyright 2014 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_provider_aura.h"
 
 #include "base/logging.h"
 #include "ui/events/event.h"
 #include "ui/events/gesture_detection/gesture_config_helper.h"
 #include "ui/events/gesture_detection/gesture_event_data.h"
 #include "ui/events/gestures/gesture_configuration.h"
 
 namespace ui {
 
 GestureProviderAura::GestureProviderAura(GestureProviderAuraClient* client)
     : client_(client),
       filtered_gesture_provider_(ui::DefaultGestureProviderConfig(), this) {
   filtered_gesture_provider_.SetDoubleTapSupportForPlatformEnabled(false);
 }
 
 GestureProviderAura::~GestureProviderAura() {}
 
 bool GestureProviderAura::OnTouchEvent(const TouchEvent& event) {
   last_touch_event_flags_ = event.flags();
+  last_touch_event_latency_info_ = *event.latency();
   bool pointer_id_is_active = false;
   for (size_t i = 0; i < pointer_state_.GetPointerCount(); ++i) {
     if (event.touch_id() != pointer_state_.GetPointerId(i))
       continue;
     pointer_id_is_active = true;
     break;
   }
 
   if (event.type() == ET_TOUCH_PRESSED && pointer_id_is_active) {
     // Ignore touch press events if we already believe the pointer is down.
@@ skipping 38 matching lines @@
                          gesture.x,
                          gesture.y,
                          last_touch_event_flags_,
                          gesture.time - base::TimeTicks(),
                          details,
                          // ui::GestureEvent stores a bitfield indicating the
                          // ids of active touch points. This is currently only
                          // used when one finger is down, and will eventually
                          // be cleaned up. See crbug.com/366707.
                          1 << gesture.motion_event_id);
+
+  ui::LatencyInfo* gesture_latency = event.latency();
+  gesture_latency->CopyLatencyFrom(
+      last_touch_event_latency_info_,

[Yufeng Shen (Slow to review), 2014/06/02 18:27:04]

so is it guaranteed that the this gesture is derived from the last_touch_event ?

[tdresser, 2014/06/02 18:30:04]

Yes, although this would attribute a gesture fired on a timer to the most recent
touch, which may or may not be what we want.

[Yufeng Shen (Slow to review), 2014/06/02 18:43:35]

Is it easy to add some latency components to the gesture that is fired on timer
using the timestamp of the timer, e.g. the ui::INPUT_EVENT_LATENCY_UI_COMPONENT
component, and here we check only if we don't have the UI component then we copy
the latency from last_touch_event ?

[tdresser, 2014/06/02 20:04:11]

I've gone with the existing Aura behavior, which is to not set any latency
components for events triggered by a timeout.

+      ui::INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT);
+  gesture_latency->CopyLatencyFrom(
+      last_touch_event_latency_info_,
+      ui::INPUT_EVENT_LATENCY_UI_COMPONENT);
+  gesture_latency->CopyLatencyFrom(
+      last_touch_event_latency_info_,
+      ui::INPUT_EVENT_LATENCY_ACKED_TOUCH_COMPONENT);
+
   client_->OnGestureEvent(&event);
 }
 
 bool GestureProviderAura::IsConsideredDoubleTap(
     const GestureEventData& previous_tap,
     const GestureEventData& current_tap) const {
   if (current_tap.time - previous_tap.time >
       base::TimeDelta::FromMilliseconds(
           ui::GestureConfiguration::max_seconds_between_double_click() *
           1000)) {
     return false;
   }
 
   double double_tap_slop_square =
       GestureConfiguration::max_distance_between_taps_for_double_tap();
   double_tap_slop_square *= double_tap_slop_square;
   const float delta_x = previous_tap.x - current_tap.x;
   const float delta_y = previous_tap.y - current_tap.y;
   return (delta_x * delta_x + delta_y * delta_y < double_tap_slop_square);
 }
 
 }  // namespace content