Allow releaseCallback to be null in JavaI420Buffer#wrap.

R=magjed

Bug: None
Change-Id: I3d57198dd0b8e0575af61b0dac439e3753a2360a
Reviewed-on: https://webrtc-review.googlesource.com/92386
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24193}

sdk/android/api/org/webrtc/JavaI420Buffer.java

@@ -50,7 +50,8 @@ public class JavaI420Buffer implements VideoFrame.I420Buffer {
 
   /** Wraps existing ByteBuffers into JavaI420Buffer object without copying the contents. */
   public static JavaI420Buffer wrap(int width, int height, ByteBuffer dataY, int strideY,
-      ByteBuffer dataU, int strideU, ByteBuffer dataV, int strideV, Runnable releaseCallback) {
+      ByteBuffer dataU, int strideU, ByteBuffer dataV, int strideV,
+      @Nullable Runnable releaseCallback) {
     if (dataY == null || dataU == null || dataV == null) {
       throw new IllegalArgumentException("Data buffers cannot be null.");
     }