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_modem_cdma_proxy.h b/mock_modem_cdma_proxy.h
index 915f1b1..7c5ddb6 100644
--- a/mock_modem_cdma_proxy.h
+++ b/mock_modem_cdma_proxy.h
@@ -17,7 +17,7 @@
 class MockModemCDMAProxy : public ModemCDMAProxyInterface {
  public:
   MockModemCDMAProxy();
-  virtual ~MockModemCDMAProxy();
+  ~MockModemCDMAProxy() override;
 
   MOCK_METHOD4(Activate, void(const std::string &carrier, Error *error,
                               const ActivationResultCallback &callback,