[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 a7425499e49cb3d79afc08f1fbff84a2c1a71dcb..bfea7399e5edbe4ffa4718e5f2e81185b044aaa8 100644
--- a/chrome/browser/media/router/media_router.mojom
+++ b/chrome/browser/media/router/media_router.mojom
@@ -43,6 +43,8 @@ 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.