Add VideoEncoderFactory::GetImplementations function.

The GetImplementations function is similar to the GetSupportedFormats function, but instead of providing one SdpVideoFormat per codec it provides one per codec implementation. These SdpVideoFormats can then be tagged so that a certain implementation can be instantiated when CreateVideoEncoder is called.

Bug: webrtc:10795
Change-Id: I79f2380aa03d75d5f9f36138625abf3543c2339d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/145215
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28553}

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

@@ -22,4 +22,14 @@ public interface VideoEncoderFactory {
    * result will be cached.
    */
   @CalledByNative VideoCodecInfo[] getSupportedCodecs();
+
+  /**
+   * Enumerates the list of supported video codecs that can also be tagged with
+   * implementation information. This method will only be called once and the
+   * result will be cached.
+   */
+  @CalledByNative
+  default VideoCodecInfo[] getImplementations() {
+    return getSupportedCodecs();
+  }
 }