Change other usages of .size() to .empty() when applicable.

remoting/jingle_glue/jingle_thread.cc

Index: remoting/jingle_glue/jingle_thread.cc
diff --git a/remoting/jingle_glue/jingle_thread.cc b/remoting/jingle_glue/jingle_thread.cc
index b8bc42874a8515f16d7170b97c451a138da3368d..9dc3915a3b9f4fc6d1fa40a8bcd1d9c2101827bb 100644
--- a/remoting/jingle_glue/jingle_thread.cc
+++ b/remoting/jingle_glue/jingle_thread.cc
@@ -163,7 +163,7 @@ void JingleThread::OnMessage(talk_base::Message* msg) {
 
   // Stop the thread only if there are no more messages left in the queue,
   // otherwise post another task to try again later.
-  if (msgq_.size() > 0 || fPeekKeep_) {
+  if (!msgq_.empty() || fPeekKeep_) {
     Post(this, kStopMessageId);
   } else {
     MessageQueue::Quit();