Add an accessibility alert for incorrect use of some accelerators.

ash/accelerators/accelerator_table.h

Index: ash/accelerators/accelerator_table.h
diff --git a/ash/accelerators/accelerator_table.h b/ash/accelerators/accelerator_table.h
index 38b156cf0ed904d97414b56efc23b52fccb4e9cb..21bbf6ae6b225ff6f0f011131198b58342e3bc71 100644
--- a/ash/accelerators/accelerator_table.h
+++ b/ash/accelerators/accelerator_table.h
@@ -192,6 +192,10 @@ ASH_EXPORT extern const size_t kNonrepeatableActionsLength;
 ASH_EXPORT extern const AcceleratorAction kActionsAllowedInAppMode[];
 ASH_EXPORT extern const size_t kActionsAllowedInAppModeLength;
 
+// Actions that require at least 1 window.
+ASH_EXPORT extern const AcceleratorAction kActionsNeedingWindow[];
+ASH_EXPORT extern const size_t kActionsNeedingWindowLength;
+
 }  // namespace ash
 
 #endif  // ASH_ACCELERATORS_ACCELERATOR_TABLE_H_