enable video capture to support sharing across multiple renderer processes

media/video/capture/video_capture_device.h

Index: media/video/capture/video_capture_device.h
===================================================================
--- media/video/capture/video_capture_device.h	(revision 106642)
+++ media/video/capture/video_capture_device.h	(working copy)
@@ -22,7 +22,6 @@
 
 class MEDIA_EXPORT VideoCaptureDevice {
  public:
-
   struct Name {
     // Friendly name of a device
     std::string device_name;
@@ -69,6 +68,8 @@
     // 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() {}