Reason for revert:
Broke downstream test that was waiting for 5 keyframes to be received within 10 seconds. Maybe the issue is that "stats_callback_->OnCompleteFrame(frame->num_references == 0, ..." was changed to "frame->is_keyframe()"?
Original issue's description:
> Request keyframes more frequently on stream start/decoding error.
>
> In this CL:
> - Added FrameObject::is_keyframe() convinience function.
> - Moved logic to request keyframes on decoding error from VideoReceived to
> VideoReceiveStream.
> - Added keyframe_required as a parameter to FrameBuffer::NextFrame.
>
> BUG=webrtc:8074
>
> Review-Url: https://codereview.webrtc.org/2993793002
> Cr-Commit-Position: refs/heads/master@{#19280}
> Committed: 26b4804358TBR=terelius@webrtc.org,stefan@webrtc.org,noahric@chromium.org,philipel@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:8074
Review-Url: https://codereview.webrtc.org/2994043002
Cr-Commit-Position: refs/heads/master@{#19295}
77a983185f