Revert 187340 "PPAPI: Remove threading options; it's always on"

ppapi/proxy/locking_resource_releaser.h

-// Copyright (c) 2013 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.
-
-#ifndef PPAPI_PROXY_LOCKING_RESOURCE_RELEASER_H_
-#define PPAPI_PROXY_LOCKING_RESOURCE_RELEASER_H_
-
-#include "ppapi/shared_impl/ppapi_globals.h"
-#include "ppapi/shared_impl/proxy_lock.h"
-#include "ppapi/shared_impl/resource_tracker.h"
-
-namespace ppapi {
-namespace proxy {
-
-// LockingResourceReleaser is a simple RAII class for releasing a resource at
-// the end of scope. This acquires the ProxyLock before releasing the resource.
-// It is for use in unit tests. Most proxy or implementation code should use
-// ScopedPPResource instead. Unit tests sometimes can't use ScopedPPResource
-// because it asserts that the ProxyLock is already held.
-class LockingResourceReleaser {
- public:
-  explicit LockingResourceReleaser(PP_Resource resource)
-      : resource_(resource) {
-  }
-  ~LockingResourceReleaser() {
-    ProxyAutoLock lock;
-    PpapiGlobals::Get()->GetResourceTracker()->ReleaseResource(resource_);
-  }
-
-  PP_Resource get() { return resource_; }
-
- private:
-  PP_Resource resource_;
-
-  DISALLOW_COPY_AND_ASSIGN(LockingResourceReleaser);
-};
-
-}  // namespace proxy
-}  // namespace ppapi
-
-#endif  // PPAPI_PROXY_LOCKING_RESOURCE_RELEASER_H_