Set the unique_event_id when converting from TouchEvent to WebTouchEvent

content/browser/renderer_host/input/touch_emulator.cc

Index: content/browser/renderer_host/input/touch_emulator.cc
diff --git a/content/browser/renderer_host/input/touch_emulator.cc b/content/browser/renderer_host/input/touch_emulator.cc
index ed9134b1d6b1b853d2e24d8ab59bcb503d047f15..425c1574a9700516aa6ebb45488f6f81fb1acd68 100644
--- a/content/browser/renderer_host/input/touch_emulator.cc
+++ b/content/browser/renderer_host/input/touch_emulator.cc
@@ -11,6 +11,7 @@
 #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"
@@ -225,6 +226,7 @@ bool TouchEmulator::HandleTouchEvent(const blink::WebTouchEvent& event) {
 
 void TouchEmulator::HandleEmulatedTouchEvent(blink::WebTouchEvent event) {
   DCHECK(gesture_provider_);
+  DCHECK_GT(event.uniqueTouchEventId, 0U);
   auto result = gesture_provider_->OnTouchEvent(MotionEventWeb(event));
   if (!result.succeeded)
     return;
@@ -344,6 +346,7 @@ void TouchEmulator::CancelTouch() {
       WebInputEvent::TouchCancel,
       (base::TimeTicks::Now() - base::TimeTicks()).InSecondsF(),
       &touch_event_);
+  touch_event_.uniqueTouchEventId = ui::GetNextTouchEventId();

[jdduke (slow), 2015/04/21 22:40:16]

Can we move this logic into |HandleEmulatedTouchEvent()| and populate the ID at
the beginning of the function? That should also cover the FillTouchEventAndPoint
case.

[lanwei, 2015/04/22 20:51:31]

I put setting uniqueTouchEventId into these two functions so we can actually
change touch_event_'s uniqueTouchEventId, but I think this does not matter
because we do not need its uniqueTouchEventId except when we use it create
MotionEventWeb object.

   DCHECK(gesture_provider_);
   if (gesture_provider_->GetCurrentDownEvent())
     HandleEmulatedTouchEvent(touch_event_);
@@ -429,6 +432,7 @@ void TouchEmulator::FillTouchEventAndPoint(const WebMouseEvent& mouse_event) {
   }
   touch_event_.touchesLength = 1;
   touch_event_.modifiers = mouse_event.modifiers;
+  touch_event_.uniqueTouchEventId = ui::GetNextTouchEventId();
   WebTouchEventTraits::ResetTypeAndTouchStates(
       eventType, mouse_event.timeStampSeconds, &touch_event_);