media: clarify frame dropping behavior for decoder output

 <p>

 Also since {@link android.os.Build.VERSION_CODES#M}, you can change the output Surface

 dynamically using {@link #setOutputSurface setOutputSurface}.

 <p>

 When rendering output to a Surface, the Surface may be configured to drop excessive frames (that

 are not consumed by the Surface in a timely manner). Or it may be configured to not drop excessive

 frames. In the latter mode if the Surface is not consuming output frames fast enough, it will

 eventually block the decoder. Prior to {@link android.os.Build.VERSION_CODES#Q} the exact behavior

 was undefined, with the exception that View surfaces (SuerfaceView or TextureView) always dropped

 excessive frames. Since {@link android.os.Build.VERSION_CODES#Q} the default behavior is to drop

 excessive frames. Applications can opt out of this behavior for non-View surfaces (such as

 ImageReader or SurfaceTexture) by targeting SDK {@link android.os.Build.VERSION_CODES#Q} and

 setting the key {@code "allow-frame-drop"} to {@code 0} in their configure format.

 <h4>Transformations When Rendering onto Surface</h4>