Add OnRemoved() in VideoCapture::EventHandler API

media/video/capture/video_capture.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.
 //
 // This file contains abstract classes used for media filter to handle video
 // capture devices.
 
 #ifndef MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_H_
 #define MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_H_
 
@@ skipping 48 matching lines @@
 
     // Notify client that video capture has been stopped.
     virtual void OnStopped(VideoCapture* capture) = 0;
 
     // Notify client that video capture has been paused.
     virtual void OnPaused(VideoCapture* capture) = 0;
 
     // Notify client that video capture has hit some error |error_code|.
     virtual void OnError(VideoCapture* capture, int error_code) = 0;
 
+    // Notify client that the client has been removed and no more calls will be
+    // received.
+    virtual void OnRemoved(VideoCapture* capture) = 0;
+
     // Notify client that a buffer is available.
     virtual void OnBufferReady(VideoCapture* capture,
                                scoped_refptr<VideoFrameBuffer> buffer) = 0;
 
     // Notify client about device info.
     virtual void OnDeviceInfoReceived(
         VideoCapture* capture,
         const VideoCaptureParams& device_info) = 0;
   };
 
   // TODO(wjia): merge with similar struct in browser process and move it to
   // video_capture_types.h.
   struct VideoCaptureCapability {
     int width;  // desired width.
     int height;  // desired height.
     int max_fps;  // desired maximum frame rate.
     int expected_capture_delay;  // expected delay in millisecond.
     media::VideoFrame::Format raw_type;  // desired video type.
     bool interlaced;  // need interlace format.
     bool resolution_fixed;  // indicate requested resolution can't be altered.
   };
 
   VideoCapture() {}
   virtual ~VideoCapture() {}
 
   // Request video capture to start capturing with |capability|.
   // Also register |handler| with video capture for event handling.
+  // |handler| must remain valid until it has received |OnRemoved()|.
   virtual void StartCapture(EventHandler* handler,
                             const VideoCaptureCapability& capability) = 0;
 
   // Request video capture to stop capturing for client |handler|.
+  // |handler| must remain valid until it has received |OnRemoved()|.
   virtual void StopCapture(EventHandler* handler) = 0;
 
   // Feed buffer to video capture when done with it.
   virtual void FeedBuffer(scoped_refptr<VideoFrameBuffer> buffer) = 0;
 
   virtual bool CaptureStarted() = 0;
   virtual int CaptureWidth() = 0;
   virtual int CaptureHeight() = 0;
   virtual int CaptureFrameRate() = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(VideoCapture);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_H_