Adds the UserInputMonitor implementation for Mac.

media/base/user_input_monitor_mac.cc

Index: media/base/user_input_monitor_mac.cc
diff --git a/media/base/user_input_monitor_mac.cc b/media/base/user_input_monitor_mac.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1fcb8789928eab7502e34701e6061d570d3f7d4f
--- /dev/null
+++ b/media/base/user_input_monitor_mac.cc
@@ -0,0 +1,71 @@
+// 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/user_input_monitor.h"
+
+#include <ApplicationServices/ApplicationServices.h>
+
+namespace media {
+namespace {
+
+class UserInputMonitorMac : public UserInputMonitor {
+ public:
+  explicit UserInputMonitorMac();

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

Doesn’t need to be explicit now, there are no arguments.

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

Done.

+  virtual ~UserInputMonitorMac();
+
+  virtual size_t GetKeyPressCount() const OVERRIDE;
+
+ private:
+  virtual void StartMouseMonitoring() OVERRIDE;
+  virtual void StopMouseMonitoring() OVERRIDE;
+  virtual void StartKeyboardMonitoring() OVERRIDE;
+  virtual void StopKeyboardMonitoring() OVERRIDE;
+
+  size_t initial_key_press_count_;

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

See previous comment about eliminating this member variable. I don’t think it’s
necessary.

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

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(UserInputMonitorMac);
+};
+
+UserInputMonitorMac::UserInputMonitorMac() : initial_key_press_count_(0) {}
+
+UserInputMonitorMac::~UserInputMonitorMac() {
+  DCHECK(!initial_key_press_count_);
+}
+
+size_t UserInputMonitorMac::GetKeyPressCount() const {
+  // Use |kCGEventSourceStateHIDSystemState| since we only want to count
+  // hardware generated events.
+  size_t total_count = CGEventSourceCounterForEventType(
+      kCGEventSourceStateHIDSystemState, kCGEventKeyDown);
+  return total_count - initial_key_press_count_;
+}
+
+// TODO(jiayl): add the impl.
+void UserInputMonitorMac::StartMouseMonitoring() {
+  NOTIMPLEMENTED();
+}
+
+// TODO(jiayl): add the impl.
+void UserInputMonitorMac::StopMouseMonitoring() {
+  NOTIMPLEMENTED();
+}
+
+void UserInputMonitorMac::StartKeyboardMonitoring() {
+  DCHECK_EQ(initial_key_press_count_, 0u);
+  initial_key_press_count_ = GetKeyPressCount();
+}
+
+void UserInputMonitorMac::StopKeyboardMonitoring() {
+  initial_key_press_count_ = 0;
+}
+
+}  // namespace
+
+scoped_ptr<UserInputMonitor> UserInputMonitor::Create(
+    const scoped_refptr<base::SingleThreadTaskRunner>& input_task_runner,
+    const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner) {
+  return scoped_ptr<UserInputMonitor>(new UserInputMonitorMac());
+}
+
+}  // namespace media