shill: Add C++11 override specifier to destructors of derived classes.

BUG=None
TEST=`USE=wimax FEATURES=test emerge-$BOARD platform2`

Change-Id: I88d4e29165869b26924cccb94ac940dc8961c312
Reviewed-on: https://chromium-review.googlesource.com/212267
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
diff --git a/mock_service.h b/mock_service.h
index 3da3dd2..c4f850e 100644
--- a/mock_service.h
+++ b/mock_service.h
@@ -24,7 +24,7 @@
               EventDispatcher *dispatcher,
               Metrics *metrics,
               Manager *manager);
-  virtual ~MockService();
+  ~MockService() override;
 
   MOCK_METHOD0(AutoConnect, void());
   MOCK_METHOD2(Connect, void(Error *error, const char *reason));