[Presentation API, MediaRouter] Routing from media sink selection to route creation.

chrome/browser/media/router/media_router_dialog_controller.cc

Index: chrome/browser/media/router/media_router_dialog_controller.cc
diff --git a/chrome/browser/media/router/media_router_dialog_controller.cc b/chrome/browser/media/router/media_router_dialog_controller.cc
index e6c36dafaddf6ee54fa9782a04bcc204bd96271e..a34d9dc55fc18346ac3f6cf3a244f8dbde666e14 100644
--- a/chrome/browser/media/router/media_router_dialog_controller.cc
+++ b/chrome/browser/media/router/media_router_dialog_controller.cc
@@ -115,6 +115,10 @@ MediaRouterDialogController::PassPresentationRequest() {
   return presentation_request_.Pass();
 }
 
+std::string MediaRouterDialogController::GetMediaSourceId() const {
+  return presentation_request_->media_source().id();
+}
+
 void MediaRouterDialogController::Reset() {
   initiator_observer_.reset();
   presentation_request_.reset();