[Media Router] Handle multiple Presentation URLs when creating routes

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/media_router/media_router_ui.h"
 
 #include <algorithm>
 #include <string>
 #include <unordered_map>
 #include <utility>
@@ skipping 70 matching lines @@
     case TAB_MIRROR:
       return base::TimeDelta::FromSeconds(kCreateRouteTimeoutSecondsForTab);
     case DESKTOP_MIRROR:
       return base::TimeDelta::FromSeconds(kCreateRouteTimeoutSecondsForDesktop);
     default:
       NOTREACHED();
       return base::TimeDelta();
   }
 }
 
+// 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(),
+                                [](const MediaSource& source) {

[mark a. foltz, 2016/12/02 20:59:09]

Is the lambda function necessary, or can you pass CanConnectToMediaSource
directly?

[zhaobin, 2016/12/02 22:50:57]

Done.

+                                  return CanConnectToMediaSource(source);
+                                });
+  return source_it != sources.end() ? *source_it : MediaSource("");
+}
+
 }  // namespace
 
 // static
 std::string MediaRouterUI::GetExtensionName(
     const GURL& gurl, extensions::ExtensionRegistry* registry) {
   if (gurl.is_empty() || !registry) return std::string();
 
   const extensions::Extension* extension =
       registry->enabled_extensions().GetExtensionOrAppByURL(gurl);
 
@@ skipping 215 matching lines @@
   }
 }
 
 void MediaRouterUI::OnDefaultPresentationChanged(
     const PresentationRequest& presentation_request) {
   std::vector<MediaSource> sources = presentation_request.GetMediaSources();
   presentation_request_.reset(new PresentationRequest(presentation_request));
   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.
+  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();
 }
 
 void MediaRouterUI::OnDefaultPresentationRemoved() {
   presentation_request_.reset();
   query_result_manager_->RemoveSourcesForCastMode(MediaCastMode::DEFAULT);
   // Register for MediaRoute updates without a media source.
   routes_observer_.reset(new UIMediaRoutesObserver(
@@ skipping 350 matching lines @@
         base::Time::Now() - start_time_);
     start_time_ = base::Time();
   }
 }
 
 void MediaRouterUI::UpdateMaxDialogHeight(int height) {
   handler_->UpdateMaxDialogHeight(height);
 }
 
 }  // namespace media_router