[Cast] Size-Adaptable platform video encoders.

media/cast/cast_sender.h

Index: media/cast/cast_sender.h
diff --git a/media/cast/cast_sender.h b/media/cast/cast_sender.h
index 1ccebd1bb5d8bec1130f3dbf2b788e05300157f5..01f6d7074f7e5ab7700cb1c4e16eb0b018fb3080 100644
--- a/media/cast/cast_sender.h
+++ b/media/cast/cast_sender.h
@@ -21,6 +21,10 @@
 #include "media/cast/cast_environment.h"
 #include "media/cast/net/cast_transport_sender.h"
 
+namespace gfx {
+class Size;
+}
+
 namespace media {
 class VideoFrame;
 
@@ -40,14 +44,17 @@ class VideoFrameInput : public base::RefCountedThreadSafe<VideoFrameInput> {
   // frames offer performance benefits, such as memory copy elimination. The
   // format is guaranteed to be I420 or NV12.
   //
-  // Not every encoder supports this method. Use |ShouldCreateOptimizedFrame|
-  // to determine if you can and should use this method. Calling
-  // this method when |ShouldCreateOptimizedFrame| is false will CHECK.
-  virtual scoped_refptr<VideoFrame> CreateOptimizedFrame(
-      base::TimeDelta timestamp) = 0;
+  // Not every encoder supports this method. Use |CanCreateOptimizedFrames| to
+  // determine if you can and should use this method.
+  //
+  // Even if |CanCreateOptimizedFrames| indicates support, there are transient
+  // conditions during a session where optimized frames cannot be provided.  In
+  // this case, the caller must be able to handle a nullptr return value.

[hubbe, 2015/02/11 00:47:53]

And do what?
Should the caller create an un-optimized frame, or should they wait?

[miu, 2015/02/11 02:14:23]

Done.

+  virtual scoped_refptr<VideoFrame> MaybeCreateOptimizedFrame(

[hubbe, 2015/02/11 00:47:54]

I think the "Maybe" is redundant.

[miu, 2015/02/11 02:14:23]

I put it in there for two reasons: 1) The naming strongly implies a nullptr can
be returned.  2) I want to break compilation on code outside of the Chromium
project that calls this method since its behavior has changed (as discussed w/
jfroy@).

+      const gfx::Size& frame_size, base::TimeDelta timestamp) = 0;
 
   // Returns true if the encoder supports creating optimized frames.
-  virtual bool SupportsCreateOptimizedFrame() const = 0;
+  virtual bool CanCreateOptimizedFrames() const = 0;
 
  protected:
   virtual ~VideoFrameInput() {}