Add an accessibility alert for incorrect use of some accelerators.

ash/default_accessibility_delegate.cc

Index: ash/default_accessibility_delegate.cc
diff --git a/ash/default_accessibility_delegate.cc b/ash/default_accessibility_delegate.cc
index bfc6b5099c6f2d7839b3c2d1bb819b1c9e5e1978..5bce4a58f3b711c5e29f18441ed48553770a77d9 100644
--- a/ash/default_accessibility_delegate.cc
+++ b/ash/default_accessibility_delegate.cc
@@ -15,7 +15,8 @@ DefaultAccessibilityDelegate::DefaultAccessibilityDelegate()
       screen_magnifier_enabled_(false),
       screen_magnifier_type_(kDefaultMagnifierType),
       large_cursor_enabled_(false),
-      autoclick_enabled_(false) {
+      autoclick_enabled_(false),
+      accessibility_alert_(A11Y_ALERT_NONE) {
 }
 
 DefaultAccessibilityDelegate::~DefaultAccessibilityDelegate() {}
@@ -83,5 +84,14 @@ double DefaultAccessibilityDelegate::GetSavedScreenMagnifierScale() {
   return std::numeric_limits<double>::min();
 }
 
+void DefaultAccessibilityDelegate::TriggerAccessibilityAlert(
+    AccessibilityAlert alert) {
+  accessibility_alert_ = alert;
+}
+
+AccessibilityAlert DefaultAccessibilityDelegate::GetLastAccessibilityAlert() {
+  return accessibility_alert_;
+}
+
 }  // namespace internal
 }  // namespace ash