Bug 1016558 - Log the critical displayport in the layers dump. r=Cwiiis

gfx/layers/LayersLogging.cpp

@@ -120,6 +120,7 @@ AppendToString(nsACString& s, const FrameMetrics& m,
   AppendToString(s, m.mViewport, "{ viewport=");
   AppendToString(s, m.GetScrollOffset(), " viewportScroll=");
   AppendToString(s, m.mDisplayPort, " displayport=");
+  AppendToString(s, m.mCriticalDisplayPort, " critdp=");
   AppendToString(s, m.mScrollableRect, " scrollableRect=");
   AppendToString(s, m.GetScrollId(), " scrollId=", " }");
   return s += sfx;