Fix self-assignment in pp::Resource

ppapi/cpp/resource.cc

 // Copyright (c) 2010 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 "ppapi/cpp/resource.h"
 
 #include <algorithm>
 
 #include "ppapi/cpp/logging.h"
 #include "ppapi/cpp/module.h"
 
 namespace pp {
 
 Resource::Resource() : pp_resource_(0) {
 }
 
 Resource::Resource(const Resource& other) : pp_resource_(other.pp_resource_) {
   if (!is_null())
     Module::Get()->core()->AddRefResource(pp_resource_);
 }
 
 Resource::~Resource() {
   if (!is_null())
     Module::Get()->core()->ReleaseResource(pp_resource_);
 }
 
 Resource& Resource::operator=(const Resource& other) {
+  if (!other.is_null())
+    Module::Get()->core()->AddRefResource(other.pp_resource_);
   if (!is_null())
     Module::Get()->core()->ReleaseResource(pp_resource_);
   pp_resource_ = other.pp_resource_;
-  if (!is_null())
-    Module::Get()->core()->AddRefResource(pp_resource_);
   return *this;
 }
 
 PP_Resource Resource::detach() {
   PP_Resource ret = pp_resource_;
   pp_resource_ = 0;
   return ret;
 }
 
 Resource::Resource(PP_Resource resource) : pp_resource_(resource) {
   if (!is_null())
     Module::Get()->core()->AddRefResource(pp_resource_);
 }
 
 void Resource::PassRefFromConstructor(PP_Resource resource) {
   PP_DCHECK(!pp_resource_);
   pp_resource_ = resource;
 }
 
 }  // namespace pp