Reland of Delete webrtc::VideoFrame methods buffer and stride. (patchset #1 id:1 of https://codereview.webrtc.org/1935443002/ )

Reason for revert:
I plan to reland this change in a week or two, after downstream users are updated.

Original issue's description:
> Revert of Delete webrtc::VideoFrame methods buffer and stride. (patchset #14 id:250001 of https://codereview.webrtc.org/1900673002/ )
>
> Reason for revert:
> Breaks chrome FYI bots.
>
> Original issue's description:
> > 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
>
> TBR=perkj@webrtc.org,magjed@webrtc.org,pbos@webrtc.org,pthatcher@webrtc.org,stefan@webrtc.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=webrtc:5682
>
> Committed: https://crrev.com/5b3c443d301f2c2f18dac5b02652c08b91ea3828
> Cr-Commit-Position: refs/heads/master@{#12558}

TBR=perkj@webrtc.org,magjed@webrtc.org,pbos@webrtc.org,pthatcher@webrtc.org,stefan@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:5682

Review-Url: https://codereview.webrtc.org/1963413004
Cr-Commit-Position: refs/heads/master@{#12721}
diff --git a/webrtc/api/java/jni/androidmediaencoder_jni.cc b/webrtc/api/java/jni/androidmediaencoder_jni.cc
index 8e9bfa3..cffc0d1 100644
--- a/webrtc/api/java/jni/androidmediaencoder_jni.cc
+++ b/webrtc/api/java/jni/androidmediaencoder_jni.cc
@@ -795,9 +795,12 @@
   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";