Coverity: Fix a pass-by-value.

ui/base/cocoa/events_mac.mm

 // 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 <Cocoa/Cocoa.h>
 
 #include "ui/base/events.h"
 
 #include "base/logging.h"
 #include "base/time.h"
@@ skipping 161 matching lines @@
   // Touch is currently unsupported.
   return 0.0;
 }
 
 bool GetScrollOffsets(const base::NativeEvent& native_event,
                       float* x_offset,
                       float* y_offset) {
   return false;
 }
 
-bool IsNoopEvent(base::NativeEvent event) {
+bool IsNoopEvent(const base::NativeEvent& event) {
   return ([event type] == NSApplicationDefined && [event subtype] == 0);
 }
 
 base::NativeEvent CreateNoopEvent() {
   return [NSEvent otherEventWithType:NSApplicationDefined
                             location:NSZeroPoint
                        modifierFlags:0
                            timestamp:[NSDate timeIntervalSinceReferenceDate]
                         windowNumber:0
                              context:nil
                              subtype:0
                                data1:0
                                data2:0];
 }
 
 }  // namespace ui