[Presentation API] 1-UA presentation support + presenter APIs.

chrome/browser/media/router/media_router.mojom

Index: chrome/browser/media/router/media_router.mojom
diff --git a/chrome/browser/media/router/media_router.mojom b/chrome/browser/media/router/media_router.mojom
index 2ab12f07185ddce82bb2a57dd5f974a0a4bd4dcb..66089aa98ba016ec078aa15a37891575e95de7ab 100644
--- a/chrome/browser/media/router/media_router.mojom
+++ b/chrome/browser/media/router/media_router.mojom
@@ -41,6 +41,8 @@ struct MediaRoute {
   string? custom_controller_path;
   // Set to true if this route should be displayed for |media_sink_id| in UI.
   bool for_display;
+  // Set to true if this route corresponds to an offscreen presentation.
+  bool is_offscreen_presentation;
 };
 
 // Notifications or an actionable events to be shown to the user.