[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..78c0d797ca99f6af2380c479bd07f2cde167234f 100644
--- a/chrome/browser/media/router/media_router_mojo_impl.cc
+++ b/chrome/browser/media/router/media_router_mojo_impl.cc
@@ -15,6 +15,7 @@
 #include "base/stl_util.h"
 #include "base/strings/stringprintf.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 +82,11 @@ MediaRouterMojoImpl::MediaRouterMojoImpl(
       current_wake_reason_(MediaRouteProviderWakeReason::TOTAL_COUNT),
       weak_factory_(this) {
   DCHECK(event_page_tracker_);
+#if defined(OS_WIN)
+  CanFirewallUseLocalPorts(
+      base::Bind(&MediaRouterMojoImpl::EnableMdnsFromFirewallCheck,
+                 weak_factory_.GetWeakPtr()));
+#endif
 }
 
 MediaRouterMojoImpl::~MediaRouterMojoImpl() {
@@ -140,6 +146,14 @@ void MediaRouterMojoImpl::RegisterMediaRouteProvider(
         callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
+#if defined(OS_WIN)
+  // The MRPM may have been upgraded or otherwise reload such that we could be
+  // seeing an MRPM that doesn't know mDNS is enabled, even if we've told a
+  // previously registered MRPM it should be enabled. Furthermore, there may be
+  // a pending request to enable mDNS, so don't clear this flag after
+  // ExecutePendingRequests().
+  is_mdns_enabled_ = false;
+#endif
   if (event_page_tracker_->IsEventPageSuspended(
           media_route_provider_extension_id_)) {
     DVLOG_WITH_INSTANCE(1)
@@ -157,6 +171,16 @@ void MediaRouterMojoImpl::RegisterMediaRouteProvider(
   callback.Run(instance_id_);
   ExecutePendingRequests();
   wakeup_attempt_count_ = 0;
+#if defined(OS_WIN)
+  // The MRPM extension already turns on mDNS discovery for platforms other than
+  // Windows. It only relies on this signalling from MR on Windows to avoid
+  // triggering a firewall prompt out of the context of MR from the user's
+  // perspective. This particular call reminds the extension to enable mDNS
+  // discovery when it wakes up, has been upgraded, etc.
+  if (should_enable_mdns_discovery_) {
+    DoEnsureMdnsDiscoveryEnabled();
+  }
+#endif
 }
 
 void MediaRouterMojoImpl::OnIssue(const interfaces::IssuePtr issue) {
@@ -402,6 +426,12 @@ void MediaRouterMojoImpl::ClearIssue(const Issue::Id& issue_id) {
   issue_manager_.ClearIssue(issue_id);
 }
 
+void MediaRouterMojoImpl::OnUserInteraction() {
+#if defined(OS_WIN)
+  EnsureMdnsDiscoveryEnabled();
+#endif
+}
+
 bool MediaRouterMojoImpl::RegisterMediaSinksObserver(
     MediaSinksObserver* observer) {
   DCHECK(thread_checker_.CalledOnValidThread());
@@ -823,6 +853,24 @@ void MediaRouterMojoImpl::DoStopObservingMediaRoutes(
   routes_queries_.erase(source_id);
 }
 
+void MediaRouterMojoImpl::EnsureMdnsDiscoveryEnabled() {

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

This code should only be called on Windows, so I have a preference to surround
it with #if defined(OS_WIN).  To make it easier to read, put this method
alongside EnableMdnsFromFirewallCheck.

+  if (is_mdns_enabled_)
+    return;
+
+  SetWakeReason(MediaRouteProviderWakeReason::ENABLE_MDNS_DISCOVERY);
+  RunOrDefer(base::Bind(&MediaRouterMojoImpl::DoEnsureMdnsDiscoveryEnabled,
+                        base::Unretained(this)));
+  should_enable_mdns_discovery_ = true;
+}
+
+void MediaRouterMojoImpl::DoEnsureMdnsDiscoveryEnabled() {
+  DVLOG_WITH_INSTANCE(1) << "DoEnsureMdnsDiscoveryEnabled";
+  if (!is_mdns_enabled_) {
+    media_route_provider_->EnableMdnsDiscovery();
+    is_mdns_enabled_ = true;
+  }
+}
+
 void MediaRouterMojoImpl::EnqueueTask(const base::Closure& closure) {
   pending_requests_.push_back(closure);
   if (pending_requests_.size() > kMaxPendingRequests) {
@@ -930,4 +978,10 @@ 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