Adds the UserInputMonitor implementation for Mac.

media/base/user_input_monitor.cc

Index: media/base/user_input_monitor.cc
diff --git a/media/base/user_input_monitor.cc b/media/base/user_input_monitor.cc
index 18b4c8060f64e34437d4e3e9222fde4d18af520a..d4a17f102f0a4ab6edcd4ae64afa41a50701bb08 100644
--- a/media/base/user_input_monitor.cc
+++ b/media/base/user_input_monitor.cc
@@ -18,7 +18,7 @@ scoped_ptr<UserInputMonitor> UserInputMonitor::Create(
 
 UserInputMonitor::~UserInputMonitor() {
   DCHECK(!monitoring_mouse_);
-  DCHECK(!monitoring_keyboard_);
+  DCHECK(!key_press_counter_references_);
 }
 
 void UserInputMonitor::AddMouseListener(MouseEventListener* listener) {
@@ -30,6 +30,7 @@ void UserInputMonitor::AddMouseListener(MouseEventListener* listener) {
     DVLOG(2) << "Started mouse monitoring.";
   }
 }
+
 void UserInputMonitor::RemoveMouseListener(MouseEventListener* listener) {
   base::AutoLock auto_lock(lock_);
   mouse_listeners_.RemoveObserver(listener);
@@ -39,30 +40,43 @@ void UserInputMonitor::RemoveMouseListener(MouseEventListener* listener) {
     DVLOG(2) << "Stopped mouse monitoring.";
   }
 }
-void UserInputMonitor::AddKeyStrokeListener(KeyStrokeListener* listener) {
+
+void UserInputMonitor::AddKeyPressCounterReference() {
   base::AutoLock auto_lock(lock_);
-  key_stroke_listeners_.AddObserver(listener);
-  if (!monitoring_keyboard_) {
+  key_press_counter_references_++;
+  if (key_press_counter_references_ == 1) {
     StartKeyboardMonitoring();
-    monitoring_keyboard_ = true;
     DVLOG(2) << "Started keyboard monitoring.";
   }
 }
-void UserInputMonitor::RemoveKeyStrokeListener(KeyStrokeListener* listener) {
+
+void UserInputMonitor::ReleaseKeyPressCounterReference() {
   base::AutoLock auto_lock(lock_);
-  key_stroke_listeners_.RemoveObserver(listener);
-  if (key_stroke_listeners_.size() == 0) {
+  DCHECK(key_press_counter_references_ > 0);
+  key_press_counter_references_--;
+  if (key_press_counter_references_ == 0) {
     StopKeyboardMonitoring();
-    monitoring_keyboard_ = false;
+    pressed_keys_.clear();
+    total_key_presses_ = 0;
     DVLOG(2) << "Stopped keyboard monitoring.";
   }
 }
 
+size_t UserInputMonitor::GetKeyPressCount() const {
+  base::AutoLock auto_lock(lock_);
+  DCHECK(key_press_counter_references_);
+  return total_key_presses_;
+}
+
 UserInputMonitor::UserInputMonitor()
-    : monitoring_mouse_(false), monitoring_keyboard_(false) {}
+    : monitoring_mouse_(false),
+      key_press_counter_references_(0),
+      total_key_presses_(0) {}
 
 void UserInputMonitor::OnMouseEvent(const SkIPoint& position) {
   base::AutoLock auto_lock(lock_);
+  if (!monitoring_mouse_)
+    return;
   FOR_EACH_OBSERVER(
       MouseEventListener, mouse_listeners_, OnMouseMoved(position));
 }
@@ -70,13 +84,15 @@ void UserInputMonitor::OnMouseEvent(const SkIPoint& position) {
 void UserInputMonitor::OnKeyboardEvent(ui::EventType event,
                                        ui::KeyboardCode key_code) {
   base::AutoLock auto_lock(lock_);
-  // Updates the pressed keys and maybe notifies the key_stroke_listeners_.
+  if (!key_press_counter_references_)
+    return;
+  // 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);
-    DVLOG(6) << "Key stroke detected.";
-    FOR_EACH_OBSERVER(KeyStrokeListener, key_stroke_listeners_, OnKeyStroke());
+    total_key_presses_++;
+    DVLOG(6) << "Key press detected, total count: " << total_key_presses_;
   } else {
     DCHECK_EQ(ui::ET_KEY_RELEASED, event);
     DCHECK(pressed_keys_.find(key_code) != pressed_keys_.end());