[Media Router] Conditionally enable mDNS on Windows.

chrome/browser/media/router/media_router_mojo_impl.h

Index: chrome/browser/media/router/media_router_mojo_impl.h
diff --git a/chrome/browser/media/router/media_router_mojo_impl.h b/chrome/browser/media/router/media_router_mojo_impl.h
index 35ca51e2c872408614870b106f10dcdf9677ca10..4c2c9d4fc17655fc98dfda10254fd81ba92d53e4 100644
--- a/chrome/browser/media/router/media_router_mojo_impl.h
+++ b/chrome/browser/media/router/media_router_mojo_impl.h
@@ -21,6 +21,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/thread_task_runner_handle.h"
+#include "build/build_config.h"
 #include "chrome/browser/media/router/issue.h"
 #include "chrome/browser/media/router/issue_manager.h"
 #include "chrome/browser/media/router/media_router.mojom.h"
@@ -98,6 +99,7 @@ class MediaRouterMojoImpl : public MediaRouterBase,
       const SendRouteMessageCallback& callback) override;
   void AddIssue(const Issue& issue) override;
   void ClearIssue(const Issue::Id& issue_id) override;
+  void OnUserInteraction() override;
 
   const std::string& media_route_provider_extension_id() const {
     return media_route_provider_extension_id_;
@@ -251,6 +253,7 @@ class MediaRouterMojoImpl : public MediaRouterBase,
   void DoStopObservingMediaSinks(const MediaSource::Id& source_id);
   void DoStartObservingMediaRoutes(const MediaSource::Id& source_id);
   void DoStopObservingMediaRoutes(const MediaSource::Id& source_id);
+  void DoEnsureMdnsDiscoveryEnabled();
 
   // Invoked when the next batch of messages arrives.
   // |route_id|: ID of route of the messages.
@@ -320,6 +323,16 @@ class MediaRouterMojoImpl : public MediaRouterBase,
   // Clears the wake reason after the extension has been awoken.
   void ClearWakeReason();
 
+  // Ensures that mDNS discovery is enabled in the MRPM extension. This can be

[mark a. foltz, 2016/03/29 00:48:20]

Surround the mDNS functions with #if defined(OS_WIN)?
I don't see them used at all if !OS_WIN.

+  // called many times but the MRPM will only be called once per registration
+  // period.
+  void EnsureMdnsDiscoveryEnabled();
+
+  // Callback used to enabled mDNS in the MRPM if a firewall prompt will not be
+  // triggered. If a firewall prompt would be triggered, enabling mDNS won't
+  // happen until the user is clearly interacting with MR.
+  void EnableMdnsFromFirewallCheck(bool firewall_can_use_local_ports);

[mark a. foltz, 2016/03/29 00:48:20]

Perhaps name it OnFirewallCheckComplete?

+
   // Pending requests queued to be executed once component extension
   // becomes ready.
   std::deque<base::Closure> pending_requests_;
@@ -381,6 +394,20 @@ class MediaRouterMojoImpl : public MediaRouterBase,
   // initial event page wakeup attempt.
   bool provider_version_was_recorded_ = false;
 
+  // A pair of flags 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. |should_enable_mdns_discovery_| can only go from
+  // |false| to |true|. |is_mdns_enabled_| is set to |false| in

[mark a. foltz, 2016/03/29 00:48:20]

Maybe qualify the last sentence with "On Windows, ..."

Also |is_mdns_enabled_| is already set to false here.  Is it set again in
RegisterMediaRouteProvider?

+  // RegisterMediaRouteProvider and only set to |true| when we successfully call
+  // the extension to enable mDNS.
+#if defined(OS_WIN)
+  bool is_mdns_enabled_ = false;
+  bool should_enable_mdns_discovery_ = false;
+#else
+  bool is_mdns_enabled_ = true;

[mark a. foltz, 2016/03/29 00:48:20]

Do these need to be defined at all if !OS_WIN?

+  bool should_enable_mdns_discovery_ = true;
+#endif
+
   base::WeakPtrFactory<MediaRouterMojoImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRouterMojoImpl);