Support using TrackedCallbacks as hints to determine the handling thread of resource reply messages

ppapi/proxy/resource_reply_thread_registrar.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_RESOURCE_REPLY_THREAD_REGISTRAR_H_
+#define PPAPI_PROXY_RESOURCE_REPLY_THREAD_REGISTRAR_H_
+
+#include <map>
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
+#include "ppapi/c/pp_resource.h"
+#include "ppapi/proxy/ppapi_proxy_export.h"
+
+
+namespace base {
+class MessageLoopProxy;
+}
+
+namespace ppapi {
+
+class TrackedCallback;
+
+namespace proxy {
+
+// ResourceReplyThreadRegistrar records the handling thread for
+// PpapiPluginMsg_ResourceReply messages.
+// This class is thread safe.
+class PPAPI_PROXY_EXPORT ResourceReplyThreadRegistrar
+    : public base::RefCountedThreadSafe<ResourceReplyThreadRegistrar> {
+ public:
+  explicit ResourceReplyThreadRegistrar(
+      scoped_refptr<base::MessageLoopProxy> default_thread);
+
+  // This method can only be called while holding the Pepper proxy lock; the
+  // other methods can be called with/without the Pepper proxy lock.
+  void Register(PP_Resource resource,
+                int32_t sequence_number,
+                scoped_refptr<TrackedCallback> reply_thread_hint);
+
+  void Unregister(PP_Resource resource);
+
+  scoped_refptr<base::MessageLoopProxy> GetTargetThreadAndUnregister(
+      PP_Resource resource,
+      int32_t sequence_number);
+
+ private:
+  friend class base::RefCountedThreadSafe<ResourceReplyThreadRegistrar>;
+
+  typedef std::map<int32_t, scoped_refptr<base::MessageLoopProxy> >
+      SequenceNumberMap;
+  typedef std::map<PP_Resource, SequenceNumberMap> ResourceMap;
+
+  ~ResourceReplyThreadRegistrar();
+
+  // The lock that protects the data members below.
+  // Please note that we should never try to acquire the Pepper proxy lock while
+  // holding |lock_|, otherwise we will cause deadlock.
+  base::Lock lock_;
+  ResourceMap map_;
+  scoped_refptr<base::MessageLoopProxy> default_thread_;
+
+  DISALLOW_COPY_AND_ASSIGN(ResourceReplyThreadRegistrar);
+};
+
+}  // namespace proxy
+}  // namespace ppapi
+
+#endif   // PPAPI_PROXY_RESOURCE_REPLY_THREAD_REGISTRAR_H_