Set the unique_event_id when converting from TouchEvent to WebTouchEvent

ui/events/event.cc

Index: ui/events/event.cc
diff --git a/ui/events/event.cc b/ui/events/event.cc
index f0804d871cd9ad9790dcdbbb3af924e42e3cc32a..d2f63ac59d00de95e5b1cf0ab58c20bd41e37c0b 100644
--- a/ui/events/event.cc
+++ b/ui/events/event.cc
@@ -110,8 +110,13 @@ bool X11EventHasNonStandardState(const base::NativeEvent& event) {
 #endif
 }
 
-unsigned long long get_next_touch_event_id() {
-  static unsigned long long id = 0;
+uint64 get_next_touch_event_id() {
+  // Set the first touch_event_id to 1 because we set id to 0 for other types
+  // of events.
+  static uint64 id = 1;
+  if (id==0)
+    id++;
+  DCHECK_NE(id, 0UL);
   return id++;
 }