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

jingle/notifier/communicator/connection_settings.cc

Index: jingle/notifier/communicator/connection_settings.cc
diff --git a/jingle/notifier/communicator/connection_settings.cc b/jingle/notifier/communicator/connection_settings.cc
index ec374cc7d9368665f98dfe51ca1b70221a4d9849..d4b764c9c89384f787ed994de914df9c1d8535a4 100644
--- a/jingle/notifier/communicator/connection_settings.cc
+++ b/jingle/notifier/communicator/connection_settings.cc
@@ -78,7 +78,7 @@ void ConnectionSettingsList::AddPermutations(const std::string& hostname,
   }
 
   // Add this list to the instance list
-  while (list_temp.size() != 0) {
+  while (!list_temp.empty()) {
     list_.push_back(list_temp[0]);
     list_temp.pop_front();
   }