Reorganize event mojom files.

ui/events/mojo/traits_test_service.mojom

 // Copyright 2016 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 ui.mojom;
 
-import "components/mus/public/interfaces/input_events.mojom";
+import "ui/events/mojo/event.mojom";
 import "ui/events/mojo/latency_info.mojom";
 
 interface TraitsTestService {
   [Sync]
-  EchoEvent(mus.mojom.Event e) => (mus.mojom.Event pass);
+  EchoEvent(Event e) => (Event pass);
 
   [Sync]
   EchoLatencyComponent(LatencyComponent l) => (LatencyComponent pass);
 
   [Sync]
   EchoLatencyComponentId(LatencyComponentId l) => (LatencyComponentId pass);
 
   [Sync]
   EchoLatencyInfo(LatencyInfo l) => (LatencyInfo pass);
 };