cast: support cursor rendering for tab capture

content/public/browser/render_widget_host_view_frame_subscriber.h

Index: content/public/browser/render_widget_host_view_frame_subscriber.h
diff --git a/content/public/browser/render_widget_host_view_frame_subscriber.h b/content/public/browser/render_widget_host_view_frame_subscriber.h
index 653316606d2ae429bd5c380c39904647b131de8d..ad78c8893083711d07cd3cba7f3c8f0ddad07dbf 100644
--- a/content/public/browser/render_widget_host_view_frame_subscriber.h
+++ b/content/public/browser/render_widget_host_view_frame_subscriber.h
@@ -41,6 +41,7 @@ class RenderWidgetHostViewFrameSubscriber {
   // invalid. There was an error during the process of frame capture or the
   // platform layer is shutting down. |timestamp| is also invalid in this case.
   typedef base::Callback<void(base::TimeTicks /* timestamp */,
+                              gfx::Rect /* region_in_frame */,

[miu, 2015/10/20 02:12:44]

Need to document this in the comments.  Something like "location within the
VideoFrame where the captured content resides, with the remaining parts of the
VideoFrame blacked-out."

[Irfan, 2015/10/21 23:01:08]

Done.

                               bool /* frame_captured */)> DeliverFrameCallback;
 
   // Called when a new frame is going to be presented at time