Eliminate implicit conversion from scoped_refptr<T> to T*

webkit/plugins/ppapi/host_globals.cc

Index: webkit/plugins/ppapi/host_globals.cc
diff --git a/webkit/plugins/ppapi/host_globals.cc b/webkit/plugins/ppapi/host_globals.cc
index 7705dccac2db47872d632e36291326e79ceda12b..12a39603ef62549ea597849d414b2f33b564743c 100644
--- a/webkit/plugins/ppapi/host_globals.cc
+++ b/webkit/plugins/ppapi/host_globals.cc
@@ -63,12 +63,12 @@ HostGlobals::~HostGlobals() {
   return &host_var_tracker_;
 }
 
-::ppapi::CallbackTracker* HostGlobals::GetCallbackTrackerForInstance(
-    PP_Instance instance) {
+scoped_refptr< ::ppapi::CallbackTracker>
+HostGlobals::GetCallbackTrackerForInstance(PP_Instance instance) {
   std::map<PP_Instance, linked_ptr<InstanceData> >::iterator found =
       instance_map_.find(instance);
   if (found == instance_map_.end())
-    return NULL;
+    return scoped_refptr< ::ppapi::CallbackTracker>;
 
   return found->second->instance->module()->GetCallbackTracker();
 }