Define a new media_cast component for iOS cast builds

media/base/video_frame.h

Index: media/base/video_frame.h
diff --git a/media/base/video_frame.h b/media/base/video_frame.h
index 1b6b349bc7d3b19bf22f21941877524f55353c64..928550cbd0724b2624f164970d8763e81f9207e6 100644
--- a/media/base/video_frame.h
+++ b/media/base/video_frame.h
@@ -108,10 +108,12 @@ class MEDIA_EXPORT VideoFrame : public base::RefCountedThreadSafe<VideoFrame> {
       base::TimeDelta timestamp,
       const ReadPixelsCB& read_pixels_cb);
 
+#if !defined(MEDIA_FOR_CAST_IOS)
   // Read pixels from the native texture backing |*this| and write
   // them to |pixels| as BGRA.  |pixels| must point to a buffer at
   // least as large as 4 * visible_rect().size().GetArea().
   void ReadPixelsFromNativeTexture(const SkBitmap& pixels);
+#endif
 
   // Wraps packed image data residing in a memory buffer with a VideoFrame.
   // The image data resides in |data| and is assumed to be packed tightly in a