Revert of Revert Make the new jitter buffer the default jitter buffer. (patchset #1 id:1 of https://codereview.chromium.org/2682073003/ )

Reason for revert:
Fix here: https://codereview.chromium.org/2708593003

Original issue's description:
> Revert Make the new jitter buffer the default jitter buffer.
>
> Speculative revert of https://codereview.chromium.org/2656983002/ to see if it fixes a downstream bug.
>
> BUG=webrtc:5514
>
> Review-Url: https://codereview.webrtc.org/2682073003
> Cr-Commit-Position: refs/heads/master@{#16492}
> Committed: https://chromium.googlesource.com/external/webrtc/+/e525d6aba634b8442a0b9c247a89a6060d225ca3

TBR=nisse@webrtc.org,stefan@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:5514

Review-Url: https://codereview.webrtc.org/2704183002
Cr-Commit-Position: refs/heads/master@{#16772}
diff --git a/webrtc/modules/video_coding/frame_buffer2.h b/webrtc/modules/video_coding/frame_buffer2.h
index 529428d..b554f5b 100644
--- a/webrtc/modules/video_coding/frame_buffer2.h
+++ b/webrtc/modules/video_coding/frame_buffer2.h
@@ -28,6 +28,7 @@
 namespace webrtc {
 
 class Clock;
+class VCMReceiveStatisticsCallback;
 class VCMJitterEstimator;
 class VCMTiming;
 
@@ -39,7 +40,8 @@
 
   FrameBuffer(Clock* clock,
               VCMJitterEstimator* jitter_estimator,
-              VCMTiming* timing);
+              VCMTiming* timing,
+              VCMReceiveStatisticsCallback* stats_proxy);
 
   virtual ~FrameBuffer();
 
@@ -141,8 +143,6 @@
 
   void UpdateJitterDelay() EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
-  void UpdateHistograms() const;
-
   void ClearFramesAndHistory() EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   FrameMap frames_ GUARDED_BY(crit_);
@@ -161,16 +161,9 @@
   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