Fixed non-speaking Sign out buttons.

ash/system/user/tray_user.cc

Index: ash/system/user/tray_user.cc
diff --git a/ash/system/user/tray_user.cc b/ash/system/user/tray_user.cc
index 8e947396c1385aa586aff3e5ab74ad4606bf430e..d55ac7da0720eee2bd1c8d9748ae44d15430dd4f 100644
--- a/ash/system/user/tray_user.cc
+++ b/ash/system/user/tray_user.cc
@@ -129,8 +129,10 @@ class UserView : public views::View,
 
   // Create container for buttons.
   void AddButtonContainer() {
-    TrayPopupLabelButton* button = new TrayPopupLabelButton(this,
-        ash::user::GetLocalizedSignOutStringForStatus(login_, true));
+    const string16 title = ash::user::GetLocalizedSignOutStringForStatus(login_,
+                                                                         true);
+    TrayPopupLabelButton* button = new TrayPopupLabelButton(this, title);
+    button->SetAccessibleName(title);
     AddChildView(button);
     signout_ = button;
   }