[Media Router] Add a presentation id to MediaRoute mapping in the MR

chrome/browser/media/router/media_router_base.cc

Index: chrome/browser/media/router/media_router_base.cc
diff --git a/chrome/browser/media/router/media_router_base.cc b/chrome/browser/media/router/media_router_base.cc
index 923afc4efc79b6e37ec7dc9f865c8d1f5b3f6c2b..7403b841767e2ce1e12c0a10cf6c7c0e136b29d4 100644
--- a/chrome/browser/media/router/media_router_base.cc
+++ b/chrome/browser/media/router/media_router_base.cc
@@ -38,6 +38,16 @@ class MediaRouterBase::InternalMediaRoutesObserver
     }
   }
 
+  const MediaRoute* GetPresentationRoute(
+      const std::string& presentation_id) const {
+    for (const auto& route : current_routes) {
+      if (route.presentation_id().value() == presentation_id)
+        return &route;
+    }
+
+    return nullptr;
+  }
+
   bool has_route;
   std::vector<MediaRoute> current_routes;
   std::vector<MediaRoute::Id> incognito_route_ids;
@@ -76,6 +86,12 @@ std::vector<MediaRoute> MediaRouterBase::GetCurrentRoutes() const {
   return internal_routes_observer_->current_routes;
 }
 
+const MediaRoute* MediaRouterBase::GetPresentationRoute(
+    const std::string& presentation_id) const {
+  DCHECK(internal_routes_observer_);
+  return internal_routes_observer_->GetPresentationRoute(presentation_id);
+}
+
 MediaRouterBase::MediaRouterBase() : initialized_(false) {}
 
 // static