Refactor media permission dispatcher class and create proxy class for non-UI threads.

content/renderer/media/media_permission_dispatcher.h

 // Copyright 2015 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.
 
+// Base class for MediaPermission implementations in content. This class allows
+// multiple pending PermissionService calls by managing callbacks for its
+// subclasses. This class is not thread safe and should only be used on one
+// thread.
+
 #ifndef CONTENT_RENDERER_MEDIA_MEDIA_PERMISSION_DISPATCHER_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_PERMISSION_DISPATCHER_H_
 
 #include <map>
 
-#include "base/threading/thread_checker.h"
-#include "content/common/content_export.h"
-#include "content/common/permission_service.mojom.h"
-#include "content/public/renderer/render_frame_observer.h"
+#include "base/memory/weak_ptr.h"
 #include "media/base/media_permission.h"
 
 namespace content {
 
-// MediaPermission implementation in content. This class is not thread safe
-// and should only be used on one thread.
-class CONTENT_EXPORT MediaPermissionDispatcher : public media::MediaPermission,
-                                                 public RenderFrameObserver {
+class MediaPermissionDispatcher
+    : public media::MediaPermission,
+      public base::SupportsWeakPtr<MediaPermissionDispatcher> {
  public:
-  explicit MediaPermissionDispatcher(RenderFrame* render_frame);
+  MediaPermissionDispatcher();
   ~MediaPermissionDispatcher() override;
 
-  // media::MediaPermission implementation.
-  void HasPermission(Type type,
-                     const GURL& security_origin,
-                     const PermissionStatusCB& permission_status_cb) override;
-  void RequestPermission(
-      Type type,
-      const GURL& security_origin,
-      const PermissionStatusCB& permission_status_cb) override;
+ protected:
+  // Register callbacks for PermissionService calls.
+  uint32_t RegisterCallback(const PermissionStatusCB& permission_status_cb);
+
+  // Deliver the permission status |granted| to the callback identified by
+  // |request_id|.
+  void DeliverResult(uint32_t request_id, bool granted);
 
  private:
   // Map of request IDs and pending PermissionStatusCBs.
   typedef std::map<uint32_t, PermissionStatusCB> RequestMap;
 

[perkj_chrome, 2015/09/22 08:24:16]

Please re-add thread checker to enforce that this is single threaded since the
base functions are still used. 
You can have a protected method tread_checker() if you want.

[guoweis_left_chromium, 2015/09/22 18:48:48]

Done.

-  // Callback for |permission_service_| calls.
-  void OnPermissionStatus(uint32_t request_id, PermissionStatus status);
-
   uint32_t next_request_id_;
   RequestMap requests_;
-  PermissionServicePtr permission_service_;
-
-  base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaPermissionDispatcher);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_PERMISSION_DISPATCHER_H_