Bug 1406872 - Remove perf monitoring code - r=jandem,Gijs

This patch removes the StopWatch code that was used in the first version of
about:performance, and not being used anymore.

Differential Revision: https://phabricator.services.mozilla.com/D7453

js/ipc/WrapperOwner.cpp

@@ -12,7 +12,6 @@
 #include "jsfriendapi.h"
 #include "js/CharacterEncoding.h"
 #include "xpcprivate.h"
-#include "CPOWTimer.h"
 #include "WrapperFactory.h"
 
 #include "nsIDocShellTreeItem.h"
@@ -149,7 +148,6 @@ const CPOWProxyHandler CPOWProxyHandler::singleton;
     return failRetVal;                                                  \
   }                                                                     \
   {                                                                     \
-    CPOWTimer timer(cx);                                                \
     return owner->call args;                                            \
   }