enable video capture to support sharing across multiple renderer processes

media/video/capture/video_capture_device.h

 // Copyright (c) 2011 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.
 //
 // VideoCaptureDevice is the abstract base class for realizing video capture
 // device support in Chromium. It provides the interface for OS dependent
 // implementations.
 // The class is created and functions are invoked on a thread owned by
 // VideoCaptureManager. Capturing is done on other threads depended on the OS
 // specific implementation.
 
 #ifndef MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_
 #define MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_
 
 #include <list>
 #include <string>
 
 #include "base/time.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 class MEDIA_EXPORT VideoCaptureDevice {
  public:
-
   struct Name {
     // Friendly name of a device
     std::string device_name;
 
     // Unique name of a device. Even if there are multiple devices with the same
     // friendly name connected to the computer this will be unique.
     std::string unique_id;
   };
   typedef std::list<Name> Names;
 
@@ skipping 26 matching lines @@
     // Captured a new video frame.
     virtual void OnIncomingCapturedFrame(const uint8* data,
                                          int length,
                                          base::Time timestamp) = 0;
     // An error has occurred that can not be handled
     // and VideoCaptureDevice must be DeAllocated.
     virtual void OnError() = 0;
     // Called when VideoCaptureDevice::Allocate has been called
     // to inform of the resulting frame size and color format.
     virtual void OnFrameInfo(const Capability& info) = 0;
+    // Notify handler of state of the device.
+    virtual void OnDeviceState(bool in_use) = 0;

[mflodman_chromium_OOO, 2011/10/26 12:34:45]

Is this needed? Previously we used the event in stop to tell the device had been
stopped.

[wjia(left Chromium), 2011/10/26 21:17:33]

in VideoCaptureDeviceLinux, its Stop() is asynchronous. The callback in
VideoCaptureManager doesn't really tell the status of device. During
VideoCaptureDeviceLinux::OnStop(), it might call observer (i.e., controller). 

 
    protected:
     virtual ~EventHandler() {}
   };
   // Creates a VideoCaptureDevice object.
   // Return NULL if the hardware is not available.
   static VideoCaptureDevice* Create(const Name& device_name);
   virtual ~VideoCaptureDevice() {}
 
   // Gets the names of all video capture devices connected to this computer.
@@ skipping 20 matching lines @@
   // state it was when created.
   virtual void DeAllocate() = 0;
 
   // Get the name of the capture device.
   virtual const Name& device_name() = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_