[Notifications] Drop tap gestures for ArcCustomNotificationView.

ui/arc/notification/arc_custom_notification_view.cc

Index: ui/arc/notification/arc_custom_notification_view.cc
diff --git a/ui/arc/notification/arc_custom_notification_view.cc b/ui/arc/notification/arc_custom_notification_view.cc
index 39c3c6e4337eb5797c2e18d6bbb02ad7862aee98..8e4fdbb5809db135a223056eb549d127e201687d 100644
--- a/ui/arc/notification/arc_custom_notification_view.cc
+++ b/ui/arc/notification/arc_custom_notification_view.cc
@@ -44,6 +44,12 @@ class ArcCustomNotificationView::EventForwarder : public ui::EventHandler {
       return;
     }
 
+    // Tap gestures are handled on the Android side, so drop them here.
+    // See crbug.com/709911.
+    if (event->type() == ui::ET_GESTURE_TAP) {
+      return;
+    }
+
     if (event->IsScrollEvent()) {
       ForwardScrollEvent(event->AsScrollEvent());
     } else if (event->IsMouseWheelEvent()) {