Delete webrtc::VideoFrame methods buffer and stride.

To make the HasOneRef/IsMutable hack work, also had to change the
video_frame_buffer method to return a const ref to a scoped_ref_ptr,
to not imply an AddRef.

BUG=webrtc:5682

Review-Url: https://codereview.webrtc.org/1900673002
Cr-Commit-Position: refs/heads/master@{#12557}
diff --git a/webrtc/api/java/jni/androidmediaencoder_jni.cc b/webrtc/api/java/jni/androidmediaencoder_jni.cc
index b7f2da4..4508bc9 100644
--- a/webrtc/api/java/jni/androidmediaencoder_jni.cc
+++ b/webrtc/api/java/jni/androidmediaencoder_jni.cc
@@ -794,9 +794,12 @@
   CHECK_EXCEPTION(jni);
   RTC_CHECK(yuv_buffer) << "Indirect buffer??";
   RTC_CHECK(!libyuv::ConvertFromI420(
-      frame.buffer(webrtc::kYPlane), frame.stride(webrtc::kYPlane),
-      frame.buffer(webrtc::kUPlane), frame.stride(webrtc::kUPlane),
-      frame.buffer(webrtc::kVPlane), frame.stride(webrtc::kVPlane),
+      frame.video_frame_buffer()->DataY(),
+      frame.video_frame_buffer()->StrideY(),
+      frame.video_frame_buffer()->DataU(),
+      frame.video_frame_buffer()->StrideU(),
+      frame.video_frame_buffer()->DataV(),
+      frame.video_frame_buffer()->StrideV(),
       yuv_buffer, width_, width_, height_, encoder_fourcc_))
       << "ConvertFromI420 failed";