Add MediaStreamSource frame rate calculation to the tracker.

content/common/media/media_param_traits.cc

Index: content/common/media/media_param_traits.cc
diff --git a/content/common/media/media_param_traits.cc b/content/common/media/media_param_traits.cc
index 405e89de17eb6ddd0bffcd292b01b3bd850ceb6c..4a7e41825f0549ac11efc778210593d217a5f59b 100644
--- a/content/common/media/media_param_traits.cc
+++ b/content/common/media/media_param_traits.cc
@@ -62,6 +62,7 @@ void ParamTraits<VideoCaptureFormat>::Write(Message* m,
   m->WriteInt(p.frame_size.width());
   m->WriteInt(p.frame_size.height());
   m->WriteFloat(p.frame_rate);
+  m->WriteInt(p.number_of_dropped_frames);
   m->WriteInt(static_cast<int>(p.pixel_format));
 }
 
@@ -72,6 +73,7 @@ bool ParamTraits<VideoCaptureFormat>::Read(const Message* m,
   if (!m->ReadInt(iter, &frame_size_width) ||
       !m->ReadInt(iter, &frame_size_height) ||
       !m->ReadFloat(iter, &r->frame_rate) ||
+      !m->ReadInt(iter, &r->number_of_dropped_frames) ||
       !m->ReadInt(iter, &pixel_format))
     return false;