[Media Router] Conditionally enable mDNS on Windows.

chrome/browser/media/router/media_router_mojo_impl.cc

Index: chrome/browser/media/router/media_router_mojo_impl.cc
diff --git a/chrome/browser/media/router/media_router_mojo_impl.cc b/chrome/browser/media/router/media_router_mojo_impl.cc
index 54c50ee20c89b837ddffe385d4c6fe37d90b0fdd..eb4b131eae5ffcf4368ddf71fb78cc7f3d359783 100644
--- a/chrome/browser/media/router/media_router_mojo_impl.cc
+++ b/chrome/browser/media/router/media_router_mojo_impl.cc
@@ -14,7 +14,9 @@
 #include "base/observer_list.h"
 #include "base/stl_util.h"
 #include "base/strings/stringprintf.h"
+#include "build/build_config.h"
 #include "chrome/browser/media/router/issues_observer.h"
+#include "chrome/browser/media/router/media_route_provider_util_win.h"
 #include "chrome/browser/media/router/media_router_factory.h"
 #include "chrome/browser/media/router/media_router_metrics.h"
 #include "chrome/browser/media/router/media_router_type_converters.h"
@@ -81,6 +83,12 @@ MediaRouterMojoImpl::MediaRouterMojoImpl(
       current_wake_reason_(MediaRouteProviderWakeReason::TOTAL_COUNT),
       weak_factory_(this) {
   DCHECK(event_page_tracker_);
+#if defined(OS_WIN)
+  should_enable_mdns_discovery_ = false;
+  CanFirewallUseLocalPorts(
+      base::Bind(&MediaRouterMojoImpl::EnableMdnsFromFirewallCheck,
+                 base::Unretained(this)));
+#endif
 }
 
 MediaRouterMojoImpl::~MediaRouterMojoImpl() {
@@ -157,6 +165,11 @@ void MediaRouterMojoImpl::RegisterMediaRouteProvider(
   callback.Run(instance_id_);
   ExecutePendingRequests();
   wakeup_attempt_count_ = 0;
+#if defined(OS_WIN)
+  if (should_enable_mdns_discovery_) {
+    media_route_provider_->EnableMdnsDiscovery();
+  }
+#endif
 }
 
 void MediaRouterMojoImpl::OnIssue(const interfaces::IssuePtr issue) {
@@ -402,6 +415,17 @@ void MediaRouterMojoImpl::ClearIssue(const Issue::Id& issue_id) {
   issue_manager_.ClearIssue(issue_id);
 }
 
+bool MediaRouterMojoImpl::should_enable_mdns_discovery() const {
+  return should_enable_mdns_discovery_;
+}
+
+void MediaRouterMojoImpl::EnsureMdnsDiscoveryEnabled() {
+  if (media_route_provider_) {
+    media_route_provider_->EnableMdnsDiscovery();

[imcheng, 2016/03/25 06:26:30]

So when this is called, it is possible that the MR extension is not loaded (with
exception being RegisterMediaRouteProvider). You will need to queue a task and
wake up the extension. See
RegisterMediaSinksObserver for example.

[btolsch, 2016/03/25 18:57:04]

Done.

+  }
+  should_enable_mdns_discovery_ = true;
+}
+
 bool MediaRouterMojoImpl::RegisterMediaSinksObserver(
     MediaSinksObserver* observer) {
   DCHECK(thread_checker_.CalledOnValidThread());
@@ -930,4 +954,11 @@ void MediaRouterMojoImpl::ClearWakeReason() {
   current_wake_reason_ = MediaRouteProviderWakeReason::TOTAL_COUNT;
 }
 
+void MediaRouterMojoImpl::EnableMdnsFromFirewallCheck(
+    bool firewall_can_use_local_ports) {
+  if (firewall_can_use_local_ports) {
+    EnsureMdnsDiscoveryEnabled();
+  }
+}
+
 }  // namespace media_router