Create new class "CastTransport", which encapsulates the message read and write event loops.

extensions/browser/api/cast_channel/cast_message_util.cc

Index: extensions/browser/api/cast_channel/cast_message_util.cc
diff --git a/extensions/browser/api/cast_channel/cast_message_util.cc b/extensions/browser/api/cast_channel/cast_message_util.cc
index 3cc5ebb2f61e6785e00ade92ea7f0fbd4db3e9e9..fe5b0e850187b7e33297091dbbb1e4f42f4e9113 100644
--- a/extensions/browser/api/cast_channel/cast_message_util.cc
+++ b/extensions/browser/api/cast_channel/cast_message_util.cc
@@ -62,6 +62,13 @@ bool MessageInfoToCastMessage(const MessageInfo& message,
   return message_proto->IsInitialized();
 }
 
+bool ValidateCastMessage(const CastMessage& message_proto) {

[mark a. foltz, 2014/09/11 06:47:45]

I think there are also restrictions on namespace (non-empty string), sourceId
and destinationId (both non-empty, with legal values).

Is the intention for this to catch all semantic errors?

[Kevin M, 2014/09/11 18:07:58]

Yes. Done.

+  return (message_proto.payload_type() == CastMessage_PayloadType_STRING &&
+          message_proto.has_payload_utf8()) ||
+         (message_proto.payload_type() == CastMessage_PayloadType_BINARY &&
+          message_proto.has_payload_binary());
+}
+
 bool CastMessageToMessageInfo(const CastMessage& message_proto,
                               MessageInfo* message) {
   DCHECK(message);