Set the unique_event_id when converting from TouchEvent to WebTouchEvent

content/browser/renderer_host/input/motion_event_web.cc

Index: content/browser/renderer_host/input/motion_event_web.cc
diff --git a/content/browser/renderer_host/input/motion_event_web.cc b/content/browser/renderer_host/input/motion_event_web.cc
index 2d276f0371ea23757ad508f23df1cdb496d015ed..432fc59b4ec37b61e9c06ef2a5505ea047d17d70 100644
--- a/content/browser/renderer_host/input/motion_event_web.cc
+++ b/content/browser/renderer_host/input/motion_event_web.cc
@@ -12,6 +12,7 @@
 #include "base/logging.h"
 #include "content/browser/renderer_host/input/web_input_event_util.h"
 #include "content/common/input/web_touch_event_traits.h"
+#include "ui/events/base_event_utils.h"
 
 using blink::WebInputEvent;
 using blink::WebTouchEvent;
@@ -63,14 +64,15 @@ int GetActionIndexFrom(const WebTouchEvent& event) {
 MotionEventWeb::MotionEventWeb(const WebTouchEvent& event)
     : event_(event),
       cached_action_(GetActionFrom(event)),
-      cached_action_index_(GetActionIndexFrom(event)) {
+      cached_action_index_(GetActionIndexFrom(event)),
+      unique_event_id_(ui::GetNextTouchEventId()) {

[jdduke (slow), 2015/04/17 20:30:01]

Shouldn't this ID come from event.uniqueTouchEventId?

[lanwei, 2015/04/20 19:58:59]

This WebTouchEvent does not have a valid unique_event_id, so we need to generate
one for MotionEventWeb.

[tdresser, 2015/04/20 20:12:09]

Shouldn't it have a valid unique_event_id?

[tdresser, 2015/04/20 20:26:20]

Lan pointed out that this isn't the case with synthesized events like touch
cancels.

   DCHECK_GT(GetPointerCount(), 0U);
 }
 
 MotionEventWeb::~MotionEventWeb() {}
 
-int MotionEventWeb::GetId() const {
-  return 0;
+uint64 MotionEventWeb::GetUniqueEventId() const {
+  return unique_event_id_;
 }
 
 MotionEventWeb::Action MotionEventWeb::GetAction() const {