Coverity: Fix a pass-by-value.

ui/base/x/events_x.cc

 // Copyright (c) 2012 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.
 
 #include "ui/base/events.h"
 
 #include <X11/Xlib.h>
 #include <X11/extensions/XInput.h>
 #include <X11/extensions/XInput2.h>
 #include <string.h>
@@ skipping 716 matching lines @@
   return CMTEventData::GetInstance()->GetGestureTimes(
       *native_event, start_time, end_time);
 }
 
 void UpdateDeviceList() {
   Display* display = GetXDisplay();
   CMTEventData::GetInstance()->UpdateDeviceList(display);
   TouchFactory::GetInstance()->UpdateDeviceList(display);
 }
 
-bool IsNoopEvent(base::NativeEvent event) {
+bool IsNoopEvent(const base::NativeEvent& event) {
 #if defined(TOOLKIT_USES_GTK)
   NOTREACHED();
   return false;
 #else
   return (event->type == ClientMessage &&
       event->xclient.message_type == GetNoopEventAtom());
 #endif
 }
 
 base::NativeEvent CreateNoopEvent() {
@@ skipping 11 matching lines @@
   NOTREACHED();
 #else
   // Make sure we use atom from current xdisplay, which may
   // change during the test.
   noop->xclient.message_type = GetNoopEventAtom();
 #endif
   return noop;
 }
 
 }  // namespace ui