Remove the proxy callback tracker.

ppapi/proxy/plugin_dispatcher.cc

Index: ppapi/proxy/plugin_dispatcher.cc
diff --git a/ppapi/proxy/plugin_dispatcher.cc b/ppapi/proxy/plugin_dispatcher.cc
index 2bed85969f0620eef890216a07a27a616c371de7..a45cc12d983bf0d95e144cfdde27aaf833a4c451 100644
--- a/ppapi/proxy/plugin_dispatcher.cc
+++ b/ppapi/proxy/plugin_dispatcher.cc
@@ -43,10 +43,18 @@ InstanceToDispatcherMap* g_instance_to_dispatcher = NULL;
 }  // namespace
 
 InstanceData::InstanceData()
-    : fullscreen(PP_FALSE), flash_fullscreen(PP_FALSE) {
+    : fullscreen(PP_FALSE),
+      flash_fullscreen(PP_FALSE),
+      mouse_lock_callback(PP_BlockUntilComplete()) {
   memset(&position, 0, sizeof(position));
 }
 
+InstanceData::~InstanceData() {
+  // Run any pending mouse lock callback to prevent leaks.
+  if (mouse_lock_callback.func)
+    PP_RunAndClearCompletionCallback(&mouse_lock_callback, PP_ERROR_ABORTED);
+}
+
 PluginDispatcher::PluginDispatcher(base::ProcessHandle remote_process_handle,
                                    GetInterfaceFunc get_interface)
     : Dispatcher(remote_process_handle, get_interface),