[Media Router] Conditionally enable mDNS on Windows.

chrome/browser/media/router/mock_media_router.h

Index: chrome/browser/media/router/mock_media_router.h
diff --git a/chrome/browser/media/router/mock_media_router.h b/chrome/browser/media/router/mock_media_router.h
index 4ab2725aa9be72840cc175bd0381120cda2cceef..bdb97f3c2bc1693d6d84932a926481f10758afee 100644
--- a/chrome/browser/media/router/mock_media_router.h
+++ b/chrome/browser/media/router/mock_media_router.h
@@ -67,6 +67,8 @@ class MockMediaRouter : public MediaRouter {
                     const SendRouteMessageCallback& callback));
   MOCK_METHOD1(AddIssue, void(const Issue& issue));
   MOCK_METHOD1(ClearIssue, void(const Issue::Id& issue_id));
+  MOCK_CONST_METHOD0(is_mdns_discovery_enabled, bool());
+  MOCK_METHOD0(EnableMdnsDiscovery, void());
   MOCK_METHOD1(OnPresentationSessionDetached,
                void(const MediaRoute::Id& route_id));
   scoped_ptr<PresentationConnectionStateSubscription>