Show overlay displaying the state of all sticky keys when it is enabled.

ash/sticky_keys/sticky_keys_controller.h

Index: ash/sticky_keys/sticky_keys_controller.h
diff --git a/ash/sticky_keys/sticky_keys_controller.h b/ash/sticky_keys/sticky_keys_controller.h
index c31eebd70a8e1ca428a959d885305fb9cc4329e0..30b0d3d1b1f2120cbeea0ed68d76e630faae2d09 100644
--- a/ash/sticky_keys/sticky_keys_controller.h
+++ b/ash/sticky_keys/sticky_keys_controller.h
@@ -6,6 +6,7 @@
 #define ASH_STICKY_KEYS_STICKY_KEYS_CONTROLLER_H_
 
 #include "ash/ash_export.h"
+#include "ash/sticky_keys/sticky_keys_constants.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/event_handler.h"
@@ -22,6 +23,7 @@ class Window;
 
 namespace ash {
 
+class StickyKeysOverlay;
 class StickyKeysHandler;
 
 // StickyKeysController is an accessibility feature for users to be able to
@@ -80,6 +82,9 @@ class ASH_EXPORT StickyKeysController : public ui::EventHandler {
   virtual void OnMouseEvent(ui::MouseEvent* event) OVERRIDE;
   virtual void OnScrollEvent(ui::ScrollEvent* event) OVERRIDE;
 
+  // Updates the overlay UI with the current state of the sticky keys.
+  void UpdateOverlay();
+
   // Whether sticky keys is activated and modifying events.
   bool enabled_;
 
@@ -88,6 +93,8 @@ class ASH_EXPORT StickyKeysController : public ui::EventHandler {
   scoped_ptr<StickyKeysHandler> alt_sticky_key_;
   scoped_ptr<StickyKeysHandler> ctrl_sticky_key_;
 
+  scoped_ptr<StickyKeysOverlay> overlay_;
+
   DISALLOW_COPY_AND_ASSIGN(StickyKeysController);
 };
 
@@ -139,22 +146,9 @@ class ASH_EXPORT StickyKeysHandler {
     virtual void DispatchScrollEvent(ui::ScrollEvent* event,
                                      aura::Window* target) = 0;
   };
-  // Represents Sticky Key state.
-  enum StickyKeyState {
-    // The sticky key is disabled. Incomming non modifier key events are not
-    // affected.
-    DISABLED,
-    // The sticky key is enabled. Incomming non modifier key down events are
-    // modified with |modifier_flag_|. After that, sticky key state become
-    // DISABLED.
-    ENABLED,
-    // The sticky key is locked. Incomming non modifier key down events are
-    // modified with |modifier_flag_|.
-    LOCKED,
-  };
 
   // This class takes an ownership of |delegate|.
-  StickyKeysHandler(ui::EventFlags modifier_flag,
+  StickyKeysHandler(StickyKeyModifier modifier,
                     StickyKeysHandlerDelegate* delegate);
   ~StickyKeysHandler();
 
@@ -207,7 +201,10 @@ class ASH_EXPORT StickyKeysHandler {
   void AppendModifier(ui::MouseEvent* event);
   void AppendModifier(ui::ScrollEvent* event);
 
-  // The modifier flag to be monitored and appended.
+  // The modifier key this handler is responsible for.
+  StickyKeyModifier modifier_;
+
+  // The modifier flag to be monitored and appended to events.
   const ui::EventFlags modifier_flag_;
 
   // The current sticky key status.