Make VideoCaptureController single-threaded and not ref counted.

content/browser/renderer_host/media/video_capture_manager.h

 // Copyright (c) 2012 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.
 
 // VideoCaptureManager is used to open/close, start/stop, enumerate available
 // video capture devices, and manage VideoCaptureController's.
 // All functions are expected to be called from Browser::IO thread. Some helper
 // functions (*OnDeviceThread) will dispatch operations to the device thread.
 // VideoCaptureManager will open OS dependent instances of VideoCaptureDevice.
 // A device can only be opened once.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_MANAGER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_MANAGER_H_
 
 #include <map>
 #include <set>
 #include <string>
 
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "base/process/process_handle.h"
 #include "content/browser/renderer_host/media/media_stream_provider.h"
 #include "content/browser/renderer_host/media/video_capture_controller_event_handler.h"
 #include "content/common/content_export.h"
 #include "content/common/media/media_stream_options.h"
 #include "media/video/capture/video_capture_device.h"
 #include "media/video/capture/video_capture_types.h"
 
 namespace content {
-class MockVideoCaptureManager;
 class VideoCaptureController;
 class VideoCaptureControllerEventHandler;
 
 // VideoCaptureManager opens/closes and start/stops video capture devices.
 class CONTENT_EXPORT VideoCaptureManager : public MediaStreamProvider {
  public:
+  // Callback used to signal the completion of a controller lookup.
+  typedef base::Callback<
+      void(const base::WeakPtr<VideoCaptureController>&)> DoneCB;

[Ami GONE FROM CHROMIUM, 2013/09/14 00:32:24]

"DoneCB"?  Oh, so your "callback" signifies being "done"?
</youdontsay>

Not that I have a fantastic alternate suggestion :(

[ncarter (slow), 2013/09/14 01:29:31]

One must pick one's battles.

+
   // Calling |Start| of this id will open the first device, even though open has
   // not been called. This is used to be able to use video capture devices
   // before MediaStream is implemented in Chrome and WebKit.
   enum { kStartOpenSessionId = 1 };
 
   VideoCaptureManager();
 
   // Implements MediaStreamProvider.
   virtual void Register(MediaStreamProviderListener* listener,
                         base::MessageLoopProxy* device_thread_loop) OVERRIDE;
@@ skipping 16 matching lines @@
   // value of |capture_params.session_id| controls which device is selected;
   // this value should be a session id previously returned by Open().
   //
   // If the device is not already started (i.e., no other client is currently
   // capturing from this device), this call will cause a VideoCaptureController
   // and VideoCaptureDevice to be created, possibly asynchronously.
   //
   // On success, the controller is returned via calling |done_cb|, indicating
   // that the client was successfully added. A NULL controller is passed to
   // the callback on failure.
-  void StartCaptureForClient(
-      const media::VideoCaptureParams& capture_params,
-      base::ProcessHandle client_render_process,
-      VideoCaptureControllerID client_id,
-      VideoCaptureControllerEventHandler* client_handler,
-      base::Callback<void(VideoCaptureController*)> done_cb);
+  void StartCaptureForClient(const media::VideoCaptureParams& capture_params,
+                             base::ProcessHandle client_render_process,
+                             VideoCaptureControllerID client_id,
+                             VideoCaptureControllerEventHandler* client_handler,
+                             DoneCB done_cb);

[Ami GONE FROM CHROMIUM, 2013/09/14 00:32:24]

Shouldn't callbacks be passed by const&?

[ncarter (slow), 2013/09/14 01:29:31]

Done.

 
   // Called by VideoCaptureHost to remove |client_handler|. If this is the last
   // client of the device, the |controller| and its VideoCaptureDevice may be
   // destroyed. The client must not access |controller| after calling this
   // function.
   void StopCaptureForClient(VideoCaptureController* controller,
                             VideoCaptureControllerID client_id,
                             VideoCaptureControllerEventHandler* client_handler);
 
  private:
   virtual ~VideoCaptureManager();
   struct DeviceEntry;
 
   // Helper for the kStartOpenSessionId case.
   void OpenAndStartDefaultSession(
       const media::VideoCaptureParams& capture_params,
       base::ProcessHandle client_render_process,
       VideoCaptureControllerID client_id,
       VideoCaptureControllerEventHandler* client_handler,
-      base::Callback<void(VideoCaptureController*)> done_cb,
+      DoneCB done_cb,
       const media::VideoCaptureDevice::Names& device_names);
 
   // Helper routine implementing StartCaptureForClient().
   void DoStartCaptureForClient(
       const media::VideoCaptureParams& capture_params,
       base::ProcessHandle client_render_process,
       VideoCaptureControllerID client_id,
       VideoCaptureControllerEventHandler* client_handler,
-      base::Callback<void(VideoCaptureController*)> done_cb);
+      DoneCB done_cb);
 
   // Check to see if |entry| has no clients left on its controller. If so,
   // remove it from the list of devices, and delete it asynchronously. |entry|
   // may be freed by this function.
   void DestroyDeviceEntryIfNoClients(DeviceEntry* entry);
 
   // Helpers to report an event to our Listener.
   void OnOpened(MediaStreamType type, int capture_session_id);
   void OnClosed(MediaStreamType type, int capture_session_id);
   void OnDevicesEnumerated(MediaStreamType stream_type,
@@ skipping 11 matching lines @@
   DeviceEntry* GetDeviceEntryForController(
       const VideoCaptureController* controller);
 
   bool IsOnDeviceThread() const;
 
   // Queries and returns the available device IDs.
   media::VideoCaptureDevice::Names GetAvailableDevicesOnDeviceThread(
       MediaStreamType stream_type);
 
   // Create and Start a new VideoCaptureDevice, storing the result in
-  // |entry->video_capture_device|.
+  // |entry->video_capture_device|. Ownership of |handler| passes to
+  // the device.
   void DoStartDeviceOnDeviceThread(
       DeviceEntry* entry,
       const media::VideoCaptureCapability& capture_params,
-      media::VideoCaptureDevice::EventHandler* controller_as_handler);
+      scoped_ptr<media::VideoCaptureDevice::EventHandler> handler);
 
   // Stop and destroy the VideoCaptureDevice held in
   // |entry->video_capture_device|.
   void DoStopDeviceOnDeviceThread(DeviceEntry* entry);
 
-  // Helper to clean up the DeviceEntry* instance, and the
-  // VideoCaptureController, on the IO thread. Must happen after
-  // DoStopDeviceOnDeviceThread() destroys the VideoCaptureDevice. It is assumed
-  // that |dead_device| has already been removed from the |devices_| map.
-  void FreeDeviceEntryOnIOThread(scoped_ptr<DeviceEntry> dead_device);
-
   // The message loop of media stream device thread, where VCD's live.
   scoped_refptr<base::MessageLoopProxy> device_loop_;
 
   // Only accessed on Browser::IO thread.
   MediaStreamProviderListener* listener_;
   int new_capture_session_id_;
 
   // An entry is kept in this map for every session that has been created via
   // the Open() entry point. The keys are session_id's. This map is used to
   // determine which device to use when StartCaptureForClient() occurs. Used
   // only on the IO thread.
   std::map<int, MediaStreamDevice> sessions_;
 
   // An entry, kept in a map, that owns a VideoCaptureDevice and its associated
   // VideoCaptureController. VideoCaptureManager owns all VideoCaptureDevices
   // and VideoCaptureControllers and is responsible for deleting the instances
   // when they are not used any longer.
   //
   // The set of currently started VideoCaptureDevice and VideoCaptureController
   // objects is only accessed from IO thread, though the DeviceEntry instances
   // themselves may visit to the device thread for device creation and
   // destruction.
   struct DeviceEntry {
     DeviceEntry(MediaStreamType stream_type,
                 const std::string& id,
-                scoped_refptr<VideoCaptureController> controller);
+                scoped_ptr<VideoCaptureController> controller);
     ~DeviceEntry();
 
     const MediaStreamType stream_type;
     const std::string id;
 
     // The controller. Only used from the IO thread.
-    scoped_refptr<VideoCaptureController> video_capture_controller;
+    scoped_ptr<VideoCaptureController> video_capture_controller;
 
     // The capture device. Only used from the device thread.
     scoped_ptr<media::VideoCaptureDevice> video_capture_device;
   };
   typedef std::set<DeviceEntry*> DeviceEntries;
   DeviceEntries devices_;
 
   // Set to true if using fake video capture devices for testing, false by
   // default. This is only used for the MEDIA_DEVICE_VIDEO_CAPTURE device type.
   bool use_fake_device_;
 
   // We cache the enumerated video capture devices in
   // GetAvailableDevicesOnDeviceThread() and then later look up the requested ID
   // when a device is created in DoStartDeviceOnDeviceThread(). Used only on the
   // device thread.
   media::VideoCaptureDevice::Names video_capture_devices_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoCaptureManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_MANAGER_H_