Refcount touch tracking ids to prevent freeing them too early.

ui/events/x/touch_factory_x11.cc

 // Copyright (c) 2012 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/x/touch_factory_x11.h"
 
 #include <X11/Xatom.h>
 #include <X11/cursorfont.h>
 #include <X11/extensions/XInput.h>
 #include <X11/extensions/XInput2.h>
@@ skipping 236 matching lines @@
   if (!id_generator_.HasGeneratedIDFor(tracking_id))
     return false;
   *slot = static_cast<int>(id_generator_.GetGeneratedID(tracking_id));
   return true;
 }
 
 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() {
   return !touch_events_disabled_ && touch_device_available_;
 }
 
 int TouchFactory::GetMaxTouchPoints() const {
   return max_touch_points_;
 }
 
@@ skipping 53 matching lines @@
       if (ptr[0] || ptr[1])
         touchscreen_ids_.insert(std::make_pair(ptr[0], ptr[1]));
     }
     XFree(prop_return);
   }
 
   XCloseDevice(display, device);
 }
 
 }  // namespace ui