Attempting to reland the Overview Button Change.

ash/system/status_area_widget.h

Index: ash/system/status_area_widget.h
diff --git a/ash/system/status_area_widget.h b/ash/system/status_area_widget.h
index f73ce22a8047ad1ee57e1e1d93158f302aab9c3a..ad1c6dd5cdad4f33ae8ef81a81cff882c61f8418 100644
--- a/ash/system/status_area_widget.h
+++ b/ash/system/status_area_widget.h
@@ -12,6 +12,7 @@
 
 namespace ash {
 
+class OverviewButtonTray;
 class ShellDelegate;
 class SystemTray;
 class WebNotificationTray;
@@ -56,6 +57,9 @@ class ASH_EXPORT StatusAreaWidget : public views::Widget {
   WebNotificationTray* web_notification_tray() {
     return web_notification_tray_;
   }
+  OverviewButtonTray* overview_button_tray() {
+    return overview_button_tray_;
+  }
 
   user::LoginStatus login_status() const { return login_status_; }
 
@@ -77,9 +81,11 @@ class ASH_EXPORT StatusAreaWidget : public views::Widget {
   void AddLogoutButtonTray();
   void AddVirtualKeyboardTray();
 #endif
+  void AddOverviewButtonTray();
 
   // Weak pointers to View classes that are parented to StatusAreaWidget:
   internal::StatusAreaWidgetDelegate* status_area_widget_delegate_;
+  OverviewButtonTray* overview_button_tray_;
   SystemTray* system_tray_;
   WebNotificationTray* web_notification_tray_;
 #if defined(OS_CHROMEOS)