exo: Use WMHelper to access ash accessibility related features.

components/exo/wm_helper.h

Index: components/exo/wm_helper.h
diff --git a/components/exo/wm_helper.h b/components/exo/wm_helper.h
index 69798803792ddb82bd4eafa675ee77b7b48e2210..306c1f11c565eea0ba3467df2e9bd63c91b0e5ed 100644
--- a/components/exo/wm_helper.h
+++ b/components/exo/wm_helper.h
@@ -62,6 +62,14 @@ class WMHelper {
     virtual ~MaximizeModeObserver() {}
   };
 
+  class AccessibilityObserver {
+   public:
+    virtual void OnAccessibilityModeChanged() = 0;
+
+   protected:
+    virtual ~AccessibilityObserver() {}
+  };
+
   virtual ~WMHelper();
 
   static void SetInstance(WMHelper* helper);
@@ -75,6 +83,8 @@ class WMHelper {
   void RemoveCursorObserver(CursorObserver* observer);
   void AddMaximizeModeObserver(MaximizeModeObserver* observer);
   void RemoveMaximizeModeObserver(MaximizeModeObserver* observer);
+  void AddAccessibilityObserver(AccessibilityObserver* observer);
+  void RemoveAccessibilityObserver(AccessibilityObserver* observer);
 
   virtual const display::ManagedDisplayInfo GetDisplayInfo(
       int64_t display_id) const = 0;
@@ -88,6 +98,8 @@ class WMHelper {
   virtual void AddPostTargetHandler(ui::EventHandler* handler) = 0;
   virtual void RemovePostTargetHandler(ui::EventHandler* handler) = 0;
   virtual bool IsMaximizeModeWindowManagerEnabled() const = 0;
+  virtual bool IsSpokenFeedbackEnabled() const = 0;
+  virtual void PlayEarcon(int sound_key) const = 0;
 
  protected:
   WMHelper();
@@ -100,12 +112,14 @@ class WMHelper {
   void NotifyCursorSetChanged(ui::CursorSetType cursor_set);
   void NotifyMaximizeModeStarted();
   void NotifyMaximizeModeEnded();
+  void NotifyAccessibilityModeChanged();
 
  private:
   base::ObserverList<ActivationObserver> activation_observers_;
   base::ObserverList<FocusObserver> focus_observers_;
   base::ObserverList<CursorObserver> cursor_observers_;
   base::ObserverList<MaximizeModeObserver> maximize_mode_observers_;
+  base::ObserverList<AccessibilityObserver> accessibility_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(WMHelper);
 };