Set the unique_event_id when converting from TouchEvent to WebTouchEvent

content/browser/renderer_host/input/touch_emulator.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 "content/browser/renderer_host/input/touch_emulator.h"
 
 #include "content/browser/renderer_host/input/motion_event_web.h"
 #include "content/browser/renderer_host/input/web_input_event_util.h"
 #include "content/common/input/web_touch_event_traits.h"
 #include "content/grit/content_resources.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_switches.h"
 #include "third_party/WebKit/public/platform/WebCursorInfo.h"
+#include "ui/events/base_event_utils.h"
 #include "ui/events/blink/blink_event_util.h"
 #include "ui/events/gesture_detection/gesture_provider_config_helper.h"
 #include "ui/gfx/image/image.h"
 #include "ui/gfx/screen.h"
 
 using blink::WebGestureEvent;
 using blink::WebInputEvent;
 using blink::WebKeyboardEvent;
 using blink::WebMouseEvent;
 using blink::WebMouseWheelEvent;
@@ skipping 194 matching lines @@
   if (!native_stream_active_sequence_count_ && !is_sequence_start)
     return true;
 
   if (is_sequence_start)
     native_stream_active_sequence_count_++;
   return false;
 }
 
 void TouchEmulator::HandleEmulatedTouchEvent(blink::WebTouchEvent event) {
   DCHECK(gesture_provider_);
+  event.uniqueTouchEventId = ui::GetNextTouchEventId();

[sadrul, 2015/04/23 16:56:23]

Should this happen in WebTouchEventTraits::ResetTypeAndTouchStates() instead?

[lanwei, 2015/04/24 20:21:09]

Tim pointed out that ResetTypeAndTouchStates may be called multiple times and
HandleEmulatedTouchEvent will only be called once, so it is safe to put it here.
We add this setting uniqueTouchEventId here is because this MotionEventWeb
object is generated from WebTouchEvent object which does not have a valid
uniqueTouchEventId. Normally WebTouchEvent are generated from MotionEvent which
are from TouchEvent, which will have a valid uniqueTouchEventId.

[tdresser, 2015/04/27 14:02:24]

Currently we only call ResetTypeAndTouchStates once per event, but I can picture
us introducing bugs by later calling ResetTypeAndTouchStates multiple times. It
seems unlikely that we'd switch to calling HandleEmulatedTouchEvent multiple
times per event.

We could move this to ResetTypeAndTouchStates, and DCHECK that the
uniqueTouchEventId is unset before generating a new one, but this seems more
straight forward to me.

   auto result = gesture_provider_->OnTouchEvent(MotionEventWeb(event));
   if (!result.succeeded)
     return;
 
   const bool event_consumed = true;
   // Block emulated event when emulated native stream is active.
   if (native_stream_active_sequence_count_) {
     gesture_provider_->OnSyncTouchEventAck(event_consumed);
     return;
   }
@@ skipping 204 matching lines @@
   point.screenPosition.x = mouse_event.globalX;
   point.position.y = mouse_event.y;
   point.screenPosition.y = mouse_event.globalY;
 }
 
 bool TouchEmulator::InPinchGestureMode() const {
   return shift_pressed_;
 }
 
 }  // namespace content