Improve probing by ignoring small packets which otherwise break the mechanism.

webrtc/modules/pacing/bitrate_prober.h

Index: webrtc/modules/pacing/bitrate_prober.h
diff --git a/webrtc/modules/pacing/bitrate_prober.h b/webrtc/modules/pacing/bitrate_prober.h
index b3f52afeb6ed4ed5d5bd983424c1bc3216794bca..c26b0d62753b10b31109ede5b989ce113edf30c7 100644
--- a/webrtc/modules/pacing/bitrate_prober.h
+++ b/webrtc/modules/pacing/bitrate_prober.h
@@ -22,6 +22,8 @@ namespace webrtc {
 // on being protected by the caller.
 class BitrateProber {
  public:
+  static const size_t kMinProbePacketSize;
+
   BitrateProber();
 
   void SetEnabled(bool enable);