Adds the UserInputMonitor implementation for Mac.

media/base/keyboard_event_counter.h

+// 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.
+
+#ifndef MEDIA_BASE_KEYBOARD_EVENT_COUNTER_H_
+#define MEDIA_BASE_KEYBOARD_EVENT_COUNTER_H_
+
+#include <set>
+#include "base/synchronization/lock.h"

[Mark Mentovai, 2013/08/23 20:18:11]

Blank line before this.

[jiayl, 2013/08/23 23:47:58]

Done.

+#include "ui/base/events/event_constants.h"
+#include "ui/base/keycodes/keyboard_codes.h"
+
+namespace media {
+
+// This class tracks the total number key presses based on the OnKeyboardEvent

[Mark Mentovai, 2013/08/23 20:18:11]

total number of keypresses

[jiayl, 2013/08/23 23:47:58]

Done.

+// calls it receives from the client.
+// Multiple key down events for the same key is counted as one keypress until

[Mark Mentovai, 2013/08/23 20:18:11]

is → are

[jiayl, 2013/08/23 23:47:58]

Done.

+// the same key is released.
+// Thread safe.
+class KeyboardEventCounter {
+ public:
+  KeyboardEventCounter();
+  ~KeyboardEventCounter();
+
+  // Resets the count to 0.
+  void Reset();
+  // Returns the total number of keypresses since its creation or last Reset()

[Mark Mentovai, 2013/08/23 20:18:11]

Put blank lines before the comments that introduce new things to avoid having
them vanish in between  unrelated declarations. Same on lines 30 and 36.

[jiayl, 2013/08/23 23:47:58]

Done.

+  // call.
+  size_t GetKeyPressCount() const;
+  // The client should call this method on key down or key up events.
+  void OnKeyboardEvent(ui::EventType event, ui::KeyboardCode key_code);
+
+ private:
+  // "mutable" for GetKeyPressCount().
+  mutable base::Lock lock_;
+  // The set of keys currently held down.
+  std::set<int> pressed_keys_;

[Mark Mentovai, 2013/08/23 20:18:11]

ui::KeyboardCode, not int?

[jiayl, 2013/08/23 23:47:58]

Done.

+  size_t total_key_presses_;
+
+  DISALLOW_COPY_AND_ASSIGN(KeyboardEventCounter);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_KEYBOARD_EVENT_COUNTER_H_