Add a button on status bar to indicate that accessibility is enabled.

chrome/browser/chromeos/status/status_area_view.h

Index: chrome/browser/chromeos/status/status_area_view.h
diff --git a/chrome/browser/chromeos/status/status_area_view.h b/chrome/browser/chromeos/status/status_area_view.h
index ec43087cfb9308eedd518892d41b01202319d1ed..eb1ddffa81d56efb3aed465f5bea766e1d0bd7e8 100644
--- a/chrome/browser/chromeos/status/status_area_view.h
+++ b/chrome/browser/chromeos/status/status_area_view.h
@@ -12,6 +12,7 @@
 
 namespace chromeos {
 
+class AccessibilityMenuButton;
 class CapsLockMenuButton;
 class ClockMenuButton;
 class InputMethodMenuButton;
@@ -45,6 +46,7 @@ class StatusAreaView : public AccessiblePaneView {
  private:
   StatusAreaHost* host_;
 
+  AccessibilityMenuButton* accessibility_view_;
   CapsLockMenuButton* caps_lock_view_;
   ClockMenuButton* clock_view_;
   InputMethodMenuButton* input_method_view_;