Non-Local Join for Media Router and Presentation API

chrome/browser/media/router/media_routes_observer.h

 // 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.
 
 #ifndef CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTES_OBSERVER_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTES_OBSERVER_H_
 
 #include <vector>
 
 #include "base/macros.h"
 #include "chrome/browser/media/router/media_route.h"
 
 namespace media_router {
 
 class MediaRouter;
 
 // Base class for observing when the set of MediaRoutes and their associated
 // MediaSinks have been updated.
 class MediaRoutesObserver {
  public:
-  explicit MediaRoutesObserver(MediaRouter* router);
+  explicit MediaRoutesObserver(MediaRouter* router,
+      const MediaSource::Id source_id = MediaSource::Id());
   virtual ~MediaRoutesObserver();
 
   // Invoked when the list of routes and their associated sinks have been
-  // updated.
+  // updated with the context of the |source_id|.  This will return a list of
+  // |routes| and a list of |joinable_route_ids|.  A route is joinable only if
+  // it is joinable in the context of the |source_id|.
   // Implementations may not perform operations that modify the Media Router's
   // observer list. In particular, invoking this observer's destructor within
   // OnRoutesUpdated will result in undefined behavior.
-  virtual void OnRoutesUpdated(const std::vector<MediaRoute>& routes) {}
+  virtual void OnRoutesUpdated(
+      const std::vector<MediaRoute>& routes,
+      const std::vector<MediaRoute::Id>& joinable_route_ids) {}
+
+  const MediaSource::Id source_id() const { return source_id_; }
 
  private:
   MediaRouter* router_;

[imcheng, 2015/12/01 23:45:06]

would it be possible to make this MediaRouter* const router_; ?

[matt.boetger, 2015/12/03 01:19:20]

No.  I tried and it started cascading the change down.  If we mark this as
const, then RegisterMediaRoutesObserver must be marked as const (as called from
media_routes_observer.cc:17).  If that's marked as const - then the "add" to
routes_queries (as called from media_router_mojo_impl.cc:468) must be marked as
const - which can't happen since it's base::ScopedPtrHashMap.

+  const MediaSource::Id source_id_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRoutesObserver);
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTES_OBSERVER_H_