Reorganize event mojom files.

ui/events/mojo/event_constants.mojom

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-module mus.mojom;
+module ui.mojom;
 
 // Denotes during which phase of event targeting that an accelerator will be
 // notified of an event. PRE_TARGET will be notified instead of the target
 // window. POST_TARGET will be notified after the target window, and only if the
 // event was not consumed by the target.
 enum AcceleratorPhase {
   PRE_TARGET,
   POST_TARGET,
 };
 
@@ skipping 39 matching lines @@
   PEN,
   TOUCH,
 };
 
 enum WheelMode {
   PIXEL,
   LINE,
   PAGE,
   SCALING,
 };