[Media Router] Conditionally enable mDNS on Windows.

chrome/browser/media/router/media_router_mojo_impl.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_MOJO_IMPL_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_MOJO_IMPL_H_
 
 #include <stdint.h>
 
 #include <deque>
@@ skipping 80 matching lines @@
   void DetachRoute(const MediaRoute::Id& route_id) override;
   void SendRouteMessage(const MediaRoute::Id& route_id,
                         const std::string& message,
                         const SendRouteMessageCallback& callback) override;
   void SendRouteBinaryMessage(
       const MediaRoute::Id& route_id,
       scoped_ptr<std::vector<uint8_t>> data,
       const SendRouteMessageCallback& callback) override;
   void AddIssue(const Issue& issue) override;
   void ClearIssue(const Issue::Id& issue_id) override;
+  bool should_enable_mdns_discovery() const override;
+  void EnableMdnsDiscovery() override;
 
   const std::string& media_route_provider_extension_id() const {
     return media_route_provider_extension_id_;
   }
 
   void set_instance_id_for_test(const std::string& instance_id) {
     instance_id_ = instance_id;
   }
 
  private:
@@ skipping 263 matching lines @@
   int wakeup_attempt_count_ = 0;
 
   // Records the current reason the extension is being woken up.  Is set to
   // MediaRouteProviderWakeReason::TOTAL_COUNT if there is no pending reason.
   MediaRouteProviderWakeReason current_wake_reason_;
 
   // A flag to ensure that we record the provider version once, during the
   // initial event page wakeup attempt.
   bool provider_version_was_recorded_ = false;
 
+  // A flag to ensure that mDNS discovery is only enabled on Windows when there
+  // will be appropriate context for the user to associate a firewall prompt
+  // with Media Router. This can be set to |true| earlier if we know that a
+  // prompt will not occur.
+  bool should_enable_mdns_discovery_ = true;
+
   base::WeakPtrFactory<MediaRouterMojoImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRouterMojoImpl);
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_MOJO_IMPL_H_