A11y: Introduce High Contrast Mode and Screen Magnifier to ubar tray.

ash/system/tray/system_tray_delegate.h

Index: ash/system/tray/system_tray_delegate.h
diff --git a/ash/system/tray/system_tray_delegate.h b/ash/system/tray/system_tray_delegate.h
index b8c7f3e0268cb4329051d8b8f9c3ae59f697fa24..f0a504a58f3ae3b520d48b57f83bded763a795c8 100644
--- a/ash/system/tray/system_tray_delegate.h
+++ b/ash/system/tray/system_tray_delegate.h
@@ -149,6 +149,9 @@ class SystemTrayDelegate {
   // Shows settings related to input methods.
   virtual void ShowIMESettings() = 0;
 
+  // Show accessilibity help.
+  virtual void ShowAccessibilityHelp() = 0;
+
   // Shows help.
   virtual void ShowHelp() = 0;