Add framerate for complete received frames to histogram stats:

"WebRTC.Video.CompleteFramesReceivedPerSecond".

BUG=crbug/419657
R=mflodman@webrtc.org, stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/32089004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7762 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/system_wrappers/interface/metrics.h

@@ -104,6 +104,9 @@
 namespace webrtc {
 namespace metrics {
 
+// Time that should have elapsed for stats that are gathered once per call.
+enum { kMinRunTimeInSeconds = 10 };
+
 class Histogram;
 
 // Functions for getting pointer to histogram (constructs or finds the named