[Media Router] Conditionally enable mDNS on Windows.

chrome/browser/media/router/media_router_metrics.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_METRICS_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_METRICS_H_
 
 #include "base/time/time.h"
 
 namespace media_router {
@@ skipping 23 matching lines @@
   DETACH_ROUTE = 5,
   START_OBSERVING_MEDIA_SINKS = 6,
   STOP_OBSERVING_MEDIA_SINKS = 7,
   START_OBSERVING_MEDIA_ROUTES = 8,
   STOP_OBSERVING_MEDIA_ROUTES = 9,
   LISTEN_FOR_ROUTE_MESSAGES = 10,
   STOP_LISTENING_FOR_ROUTE_MESSAGES = 11,
   CONNECTION_ERROR = 12,
   REGISTER_MEDIA_ROUTE_PROVIDER = 13,
   CONNECT_ROUTE_BY_ROUTE_ID = 14,
+  ENABLE_MDNS_DISCOVERY = 15,
 
   // NOTE: Add entries only immediately above this line.
-  TOTAL_COUNT = 15
+  TOTAL_COUNT = 16
 };
 
 // The possible actions a user can take while interacting with the Media Router
 // dialog.
 enum class MediaRouterUserAction {
   CHANGE_MODE = 0,
   START_LOCAL = 1,
   STOP_LOCAL = 2,
   CLOSE = 3,
   STATUS_REMOTE = 4,
@@ skipping 24 matching lines @@
 
   // Records the first action the user took after the Media Router dialog
   // opened.
   static void RecordMediaRouterInitialUserAction(
       MediaRouterUserAction action);
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_METRICS_H_