[Media Router] Conditionally enable mDNS on Windows.

chrome/browser/media/router/media_router.h

Index: chrome/browser/media/router/media_router.h
diff --git a/chrome/browser/media/router/media_router.h b/chrome/browser/media/router/media_router.h
index d932d9330a0d0469a057d29fe4bddcca1d4a315d..f1d8918a5ebc663c860d0ba1309f177229e0bea7 100644
--- a/chrome/browser/media/router/media_router.h
+++ b/chrome/browser/media/router/media_router.h
@@ -154,6 +154,13 @@ class MediaRouter : public KeyedService {
   // Clears the issue with the id |issue_id|.
   virtual void ClearIssue(const Issue::Id& issue_id) = 0;
 
+  // Returns |true| if mDNS discovery is enabled.
+  virtual bool is_mdns_discovery_enabled() const = 0;
+
+  // Enables mDNS discovery on Media Route Provider Manager.
+  // |is_mdns_discovery_enabled| should also return |true| after this call.
+  virtual void EnableMdnsDiscovery() = 0;
+
   // Adds |callback| to listen for state changes for presentation connected to
   // |route_id|. The returned Subscription object is owned by the caller.
   // |callback| will be invoked whenever there are state changes, until the