Add getSupportedCodecs to VideoDecoderFactory interface.

The default implementation of the method is to return an empty list.
Clients should update their implementations before WebRTC starts calling
this method.

Also updates internal WebRTC implentations of this interface to
implement the method.

Bug: webrtc:7925
Change-Id: I258de2f09f6d4cc5dd9f4657e5d54e8411f8f5d8
Reviewed-on: https://webrtc-review.googlesource.com/77641
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23325}

sdk/android/api/org/webrtc/VideoDecoderFactory.java

@@ -19,4 +19,12 @@ public interface VideoDecoderFactory {
    * VideoEncoderFactory.
    */
   @Nullable @CalledByNative VideoDecoder createDecoder(String codecType);
+
+  /**
+   * Enumerates the list of supported video codecs.
+   */
+  @CalledByNative
+  default VideoCodecInfo[] getSupportedCodecs() {
+    return new VideoCodecInfo[0];
+  }
 }