Uses mojom module names as Dart's package: import URI

mojo/services/window_manager/public/interfaces/window_manager_internal.mojom

Index: mojo/services/window_manager/public/interfaces/window_manager_internal.mojom
diff --git a/mojo/services/window_manager/public/interfaces/window_manager_internal.mojom b/mojo/services/window_manager/public/interfaces/window_manager_internal.mojom
index bdb655d6ff16032cef910b6babdd0a571b742814..258f89450f46b5bb3cd0762c688515bf0edd48e5 100644
--- a/mojo/services/window_manager/public/interfaces/window_manager_internal.mojom
+++ b/mojo/services/window_manager/public/interfaces/window_manager_internal.mojom
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+[DartUriBase="mojo/services/window_manager/public/interfaces"]
 module mojo;
 
 import "geometry/public/interfaces/geometry.mojom";