Set the unique_event_id when converting from TouchEvent to WebTouchEvent

ui/events/base_event_utils.cc

Index: ui/events/base_event_utils.cc
diff --git a/ui/events/base_event_utils.cc b/ui/events/base_event_utils.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d1d05d7cad5ab45d3e5debbb44072ee8f98060f9
--- /dev/null
+++ b/ui/events/base_event_utils.cc
@@ -0,0 +1,19 @@
+// Copyright 2015 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/base_event_utils.h"
+
+namespace ui {
+
+uint64 GetNextTouchEventId() {
+  // Set the first touch event ID to 1 because we set id to 0 for other types

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

Should we be asserting that we're on the UI thread? Will that mess with the
tests?

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

Done.

+  // of events.
+  static uint64 id = 1;
+  if (id==0)
+    id++;
+  return id++;
+}
+
+}  // namespace ui
+