Move timestamp_extrapolator and rtp_to_ntp to system wrapper so that it can be shared by both audio and video engine.

BUG=3111
TEST=try bots
R=mflodman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/13459004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6074 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/video_coding/main/source/timing.h b/webrtc/modules/video_coding/main/source/timing.h
index fcb0402..1dca5e6 100644
--- a/webrtc/modules/video_coding/main/source/timing.h
+++ b/webrtc/modules/video_coding/main/source/timing.h
@@ -18,7 +18,7 @@
 namespace webrtc {
 
 class Clock;
-class VCMTimestampExtrapolator;
+class TimestampExtrapolator;
 
 class VCMTiming {
  public:
@@ -101,7 +101,7 @@
   CriticalSectionWrapper* crit_sect_;
   Clock* clock_;
   bool master_;
-  VCMTimestampExtrapolator* ts_extrapolator_;
+  TimestampExtrapolator* ts_extrapolator_;
   VCMCodecTimer codec_timer_;
   uint32_t render_delay_ms_;
   uint32_t min_playout_delay_ms_;