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 e6a2fe2724cad4d1d1c03e03d2e9338c7248444b..2ad0118b031a04743e8fa36b323e5b316d91e054 100644
--- a/ui/events/x/touch_factory_x11.cc
+++ b/ui/events/x/touch_factory_x11.cc
@@ -254,8 +254,14 @@ 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() {