[Chromecast] Add API to set and clear image on video plane

This allows displaying higher-resolution imagery than the current
graphics back buffer.

Bug: 65155280
Change-Id: I1ed30b7fb16926bbfa5269d9848c7a0327658241
Reviewed-on: https://chromium-review.googlesource.com/641394Reviewed-by: Sergey Volk <servolk@chromium.org>
Commit-Queue: Luke Halliwell <halliwell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498549}

chromecast/public/cast_media_shlib.h

@@ -125,6 +125,13 @@ class CHROMECAST_EXPORT CastMediaShlib {
   static void SetPostProcessorConfig(const std::string& name,
                                      const std::string& config)
       __attribute__((__weak__));
+
+  // Only used on Chromecast: set and clear an image on the video plane.
+  // Image data is 8-bit ARGB format; |data| buffer byte length must be
+  // |width|*|height|*4. Returns whether the image could be successfully set.
+  static bool SetVideoPlaneImage(int width, int height, const uint8_t* data)
+      __attribute__((__weak__));
+  static void ClearVideoPlaneImage() __attribute__((__weak__));
 };
 
 }  // namespace media