Fixing a race in KeyboardEventCounter::Reset.

media/base/keyboard_event_counter.cc

 // Copyright 2013 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 "media/base/keyboard_event_counter.h"
 
 #include "base/atomicops.h"
 #include "base/logging.h"
 
 namespace media {
 
 KeyboardEventCounter::KeyboardEventCounter() : total_key_presses_(0) {}
 
 KeyboardEventCounter::~KeyboardEventCounter() {}
 
 void KeyboardEventCounter::Reset() {
   pressed_keys_.clear();
-  total_key_presses_ = 0;
+  base::subtle::NoBarrier_Store(
+      reinterpret_cast<base::subtle::AtomicWord*>(&total_key_presses_), 0);
 }
 
 void KeyboardEventCounter::OnKeyboardEvent(ui::EventType event,
                                            ui::KeyboardCode key_code) {
   // Updates the pressed keys and the total count of key presses.
   if (event == ui::ET_KEY_PRESSED) {
     if (pressed_keys_.find(key_code) != pressed_keys_.end())
       return;
     pressed_keys_.insert(key_code);
     base::subtle::NoBarrier_AtomicIncrement(
         reinterpret_cast<base::subtle::AtomicWord*>(&total_key_presses_), 1);
   } else {
     DCHECK_EQ(ui::ET_KEY_RELEASED, event);
     pressed_keys_.erase(key_code);
   }
 }
 
 size_t KeyboardEventCounter::GetKeyPressCount() const {
   return base::subtle::NoBarrier_Load(
       reinterpret_cast<const base::subtle::AtomicWord*>(&total_key_presses_));
 }
 
 }  // namespace media