[Media Router] Handle multiple Presentation URLs when creating routes

chrome/browser/ui/webui/media_router/media_router_ui.cc

Index: chrome/browser/ui/webui/media_router/media_router_ui.cc
diff --git a/chrome/browser/ui/webui/media_router/media_router_ui.cc b/chrome/browser/ui/webui/media_router/media_router_ui.cc
index 3374fc27a4c5285c2972b246aa0fd5e50e5f571d..3a7e8badba8e7b7be4e1ae11b18ec68b46ebb652 100644
--- a/chrome/browser/ui/webui/media_router/media_router_ui.cc
+++ b/chrome/browser/ui/webui/media_router/media_router_ui.cc
@@ -88,6 +88,15 @@ base::TimeDelta GetRouteRequestTimeout(MediaCastMode cast_mode) {
   }
 }
 
+// Returns the first source in |sources| that can be connected to by using the
+// "Cast" button in the dialog, or an empty source if there is none.  This is
+// used by the Media Router to find such a matching route if it exists.
+MediaSource GetSourceForRouteObserver(const std::vector<MediaSource>& sources) {
+  auto source_it =
+      std::find_if(sources.begin(), sources.end(), CanConnectToMediaSource);
+  return source_it != sources.end() ? *source_it : MediaSource("");
+}
+
 }  // namespace
 
 // static
@@ -323,10 +332,15 @@ void MediaRouterUI::OnDefaultPresentationChanged(
   query_result_manager_->SetSourcesForCastMode(
       MediaCastMode::DEFAULT, sources,
       presentation_request_->frame_url().GetOrigin());
-  // Register for MediaRoute updates.
-  // TODO(crbug.com/627655): Use multiple URLs.
+  // Register for MediaRoute updates.  NOTE(mfoltz): If there are multiple
+  // sources that can be connected to via the dialog, this will break.  We will
+  // need to observe multiple sources (keyed by sinks) in that case.  As this is
+  // Cast-specific for the forseeable future, it may be simpler to plumb a new
+  // observer API for this case.

[imcheng, 2016/12/05 21:58:39]

+1, A specific API to query routes joinable with a given source would help.

[zhaobin, 2016/12/06 20:06:37]

Acknowledged.

+  const MediaSource source_for_route_observer =
+      GetSourceForRouteObserver(sources);
   routes_observer_.reset(new UIMediaRoutesObserver(
-      router_, sources[0].id(),
+      router_, source_for_route_observer.id(),
       base::Bind(&MediaRouterUI::OnRoutesUpdated, base::Unretained(this))));
 
   UpdateCastModes();