NetworkChangeNotifierMac: lock access to network_reachable_ as it may be read

net/base/network_change_notifier_mac.h

Index: net/base/network_change_notifier_mac.h
diff --git a/net/base/network_change_notifier_mac.h b/net/base/network_change_notifier_mac.h
index d0f49d608e288426444b63288610a56dda9e3efb..e01e24434860d73e0fc891565b129aac2dbe3c4b 100644
--- a/net/base/network_change_notifier_mac.h
+++ b/net/base/network_change_notifier_mac.h
@@ -11,6 +11,7 @@
 
 #include "base/basictypes.h"
 #include "base/mac/scoped_cftyperef.h"
+#include "base/synchronization/lock.h"
 #include "net/base/network_change_notifier.h"
 #include "net/base/network_config_watcher_mac.h"
 
@@ -58,6 +59,7 @@ class NetworkChangeNotifierMac: public NetworkChangeNotifier {
   base::mac::ScopedCFTypeRef<CFRunLoopRef> run_loop_;
   base::mac::ScopedCFTypeRef<SCNetworkReachabilityRef> reachability_;
   bool network_reachable_;
+  mutable base::Lock network_reachable_lock_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifierMac);
 };