Add kGoogEchoCancellation to MediaConstraintsInterface.

talk/app/webrtc/mediaconstraintsinterface.cc

Index: talk/app/webrtc/mediaconstraintsinterface.cc
diff --git a/talk/app/webrtc/mediaconstraintsinterface.cc b/talk/app/webrtc/mediaconstraintsinterface.cc
index 87f7e6675481c85089420e6d2dd892ccce0a5492..99335788f6201e716be5dedfecde7dd076d13bd4 100644
--- a/talk/app/webrtc/mediaconstraintsinterface.cc
+++ b/talk/app/webrtc/mediaconstraintsinterface.cc
@@ -48,6 +48,8 @@ const char MediaConstraintsInterface::kMinFrameRate[] = "minFrameRate";
 // Audio constraints.
 const char MediaConstraintsInterface::kEchoCancellation[] =
     "googEchoCancellation";
+const char MediaConstraintsInterface::kGoogEchoCancellation[] =

[Andrew MacDonald, 2015/06/15 06:58:54]

Not for this CL of course, but should we change the other "goog" flags to be
similarly Goog prefixed? Not sure it's worth the pain ;)

[tommi, 2015/06/15 07:12:51]

Don't know if it's worth spending the time on it right now but yes it would be
good to be consistent.  I'll keep it in mind with future CLs I see in this area.
I saw a todo for removing googEchoCancellation2.  Maybe there's some cleanup
needed.

+    "googEchoCancellation";
 const char MediaConstraintsInterface::kExperimentalEchoCancellation[] =
     "googEchoCancellation2";
 const char MediaConstraintsInterface::kExtendedFilterEchoCancellation[] =