Add release callback and reference count to java EncodedImage class

Callback set by HardwareVideoEncoder, and wired to the codec's
releaseOutputBuffer. Intention is to move call of this method to the
destructor of a corresponding C++ class in a followup cl, and
eliminate an allocation and memcpy in the process.

Bug: webrtc:9378
Change-Id: I578480b63b68e6ac7a96cdde36379b3c50f05c3f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/142160
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29283}

sdk/android/src/jni/encoded_image.cc

@@ -34,8 +34,12 @@ ScopedJavaLocalRef<jobject> NativeToJavaEncodedImage(
   ScopedJavaLocalRef<jobject> qp;
   if (image.qp_ != -1)
     qp = NativeToJavaInteger(jni, image.qp_);
+  // TODO(bugs.webrtc.org/9378): Keep a reference to the C++ EncodedImage data,
+  // and use the releaseCallback to manage lifetime.
   return Java_EncodedImage_Constructor(
-      jni, buffer, static_cast<int>(image._encodedWidth),
+      jni, buffer, /*supportsRetain=*/true,
+      /*releaseCallback=*/ScopedJavaGlobalRef<jobject>(nullptr),
+      static_cast<int>(image._encodedWidth),
       static_cast<int>(image._encodedHeight),
       image.capture_time_ms_ * rtc::kNumNanosecsPerMillisec, frame_type,
       static_cast<jint>(image.rotation_), image._completeFrame, qp);