Revert of Make the new jitter buffer the default jitter buffer. (patchset #7 id:120001 of https://codereview.chromium.org/2627463004/ )

Reason for revert:
Breaks android bots.

Original issue's description:
> Make the new jitter buffer the default jitter buffer.
>
> This CL contains only the changes necessary to make the switch to the new jitter
> buffer, clean up will be done in follow up CLs.
>
> In this CL:
>  - Removed the WebRTC-NewVideoJitterBuffer experiment and made the
>    new video jitter buffer the default one.
>  - Moved WebRTC.Video.KeyFramesReceivedInPermille and
>    WebRTC.Video.JitterBufferDelayInMs to the ReceiveStatisticsProxy.
>
> BUG=webrtc:5514
>
> Review-Url: https://codereview.webrtc.org/2627463004
> Cr-Commit-Position: refs/heads/master@{#16114}
> Committed: https://chromium.googlesource.com/external/webrtc/+/0f0763d86d5d4e7f27e8dece02560e39c6da97d6

TBR=stefan@webrtc.org,terelius@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:5514

Review-Url: https://codereview.webrtc.org/2632123005
Cr-Commit-Position: refs/heads/master@{#16117}
diff --git a/webrtc/modules/video_coding/frame_buffer2.h b/webrtc/modules/video_coding/frame_buffer2.h
index d954bf2..b41ef2f 100644
--- a/webrtc/modules/video_coding/frame_buffer2.h
+++ b/webrtc/modules/video_coding/frame_buffer2.h
@@ -28,7 +28,6 @@
 namespace webrtc {
 
 class Clock;
-class VCMReceiveStatisticsCallback;
 class VCMJitterEstimator;
 class VCMTiming;
 
@@ -40,8 +39,7 @@
 
   FrameBuffer(Clock* clock,
               VCMJitterEstimator* jitter_estimator,
-              VCMTiming* timing,
-              VCMReceiveStatisticsCallback* stats_proxy);
+              VCMTiming* timing);
 
   virtual ~FrameBuffer();
 
@@ -143,6 +141,8 @@
 
   void UpdateJitterDelay() EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
+  void UpdateHistograms() const;
+
   FrameMap frames_ GUARDED_BY(crit_);
 
   rtc::CriticalSection crit_;
@@ -157,9 +157,16 @@
   int num_frames_buffered_ GUARDED_BY(crit_);
   bool stopped_ GUARDED_BY(crit_);
   VCMVideoProtection protection_mode_ GUARDED_BY(crit_);
-  VCMReceiveStatisticsCallback* const stats_callback_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(FrameBuffer);
+
+  // For WebRTC.Video.JitterBufferDelayInMs metric.
+  int64_t accumulated_delay_ = 0;
+  int64_t accumulated_delay_samples_ = 0;
+
+  // For WebRTC.Video.KeyFramesReceivedInPermille metric.
+  int64_t num_total_frames_ = 0;
+  int64_t num_key_frames_ = 0;
 };
 
 }  // namespace video_coding