Eliminate video capture thread in renderer

The main motivation of this change is to remove the video capture thread
in the renderer. All users of a video capture device already handles the
video frame on their thread. There is no need to call the clients with
an additional thread.

Summary of this change:
* Video capture thread eliminated
  VideoCaptureImpl now runs on the IO thread. Clients are called on the
  IO thread.
* Simplified VideoCaptureImplManager
  We still need to keep this object for the purpose of sharing a
  VideoCaptureImpl object with multiple clients. It should own these
  objects and maintain the usage count. A couple clean up items are done
  on this class:
  * It doesn't own the video capture thread now.
  * It is now a render thread only object.
  * It maintains refcount of a VideoCaptureImpl explicitly.
  * It is no longer refcounted.
  * Clients access it through RenderThreadImpl. Which ensures usage is
    on the render thread.
* New VideoCaptureHandle class
  Object of this class is returned by VideoCaptureImplManager to give
  access to a media::VideoCapture object. It is purely a wrapper and
  helps to do refcounting on the render thread.

Testing:
Added unit tests for VideoCaptureImplManager to test refcounting.
Also updated unit test for VideoCaptureImpl due to the threading
changes.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=244074

Review URL: https://codereview.chromium.org/120893002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244687 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 2 insertions, 2 deletions

diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 16d2cb4..c9e4142 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -431,8 +431,8 @@ class CONTENT_EXPORT RenderThreadImpl : public RenderThread,
   // Dispatches all P2P sockets.
   scoped_refptr<P2PSocketDispatcher> p2p_socket_dispatcher_;
 
-  // Used on multiple threads.
-  scoped_refptr<VideoCaptureImplManager> vc_manager_;
+  // Used on the render thread.
+  scoped_ptr<VideoCaptureImplManager> vc_manager_;
 
   // The count of RenderWidgets running through this thread.
   int widget_count_;