Refcount touch tracking ids to prevent freeing them too early.

ui/events/x/touch_factory_x11.cc

Index: ui/events/x/touch_factory_x11.cc
diff --git a/ui/events/x/touch_factory_x11.cc b/ui/events/x/touch_factory_x11.cc
index 9df436c803002538e61d8ec06b8bc48699d13ed1..536804a6cc342fd1bc5d7abcd4e5a29917868cac 100644
--- a/ui/events/x/touch_factory_x11.cc
+++ b/ui/events/x/touch_factory_x11.cc
@@ -250,8 +250,14 @@ int TouchFactory::GetSlotForTrackingID(uint32 tracking_id) {
   return id_generator_.GetGeneratedID(tracking_id);
 }
 
+void TouchFactory::AcquireSlotForTrackingID(uint32 tracking_id) {
+  tracking_id_refcounts_[tracking_id]++;
+}
+
 void TouchFactory::ReleaseSlotForTrackingID(uint32 tracking_id) {
-  id_generator_.ReleaseNumber(tracking_id);
+  tracking_id_refcounts_[tracking_id]--;
+  if (tracking_id_refcounts_[tracking_id] == 0)
+    id_generator_.ReleaseNumber(tracking_id);
 }
 
 bool TouchFactory::IsTouchDevicePresent() {