cros: Clean up screenlockPrivate plumbing.

chrome/common/extensions/api/screenlock_private.idl

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Control and monitor the screen locker.
 [permissions=screenlockPrivate, nodoc]
 namespace screenlockPrivate {
   // Supported authentication types shown on the user pod.
   // |offlinePassword|: The standard password field, which authenticates using
   //                   the user's regular password. The $(ref:onAuthAttempted)()
@@ skipping 12 matching lines @@
     // Returns true if the screen is currently locked, false otherwise.
     static void getLocked(BooleanCallback callback);
 
     // Set <code>locked=true</code> to lock the screen,
     // <code>locked=false</code> to unlock it.
     static void setLocked(boolean locked);
 
     // Show a message to the user on the unlock UI if the screen is locked.
     static void showMessage(DOMString message);
 
-    // Show a Button, an icon beside the input field on the user pod.
+    // Show a custom icon beside the input field on the user pod.
     // |icon|: An extension resource of the icon image.
-    static void showButton(DOMString icon);
+    static void showCustomIcon(DOMString icon);
 
-    // Hides the button added by $(ref:showButton)().
-    static void hideButton();
+    // Hides the custom icon added by $(ref:showCustomIcon)().
+    static void hideCustomIcon();
 
     // Returns the current auth type used for the user pod.
     static void getAuthType(AuthTypeCallback callback);
 
     // Set the type of the authentication for the user pod. The input field
     // area of the user pod below the user's portrait will be changed.
     // |authType|: The type of authentication to use.
     // |initialValue|: The initial value to populate the input field.
     static void setAuthType(AuthType authType, optional DOMString initialValue);
 
     // Accepts or rejects the current auth attempt.
     static void acceptAuthAttempt(boolean accept);
   };
 
   interface Events {
     // Fires whenever the screen is locked or unlocked.
     static void onChanged(boolean locked);
 
-    // Fires when the user clicks on the Button shown by $(ref:showButton)().
-    static void onButtonClicked();
-
     // Fires when the user attempts to authenticate with the user's input.
     // There will be at most one auth attempt active at any time.
     // Call $(ref:acceptAuthAttempt)() to accept or reject this attempt.
     // Note: Some authentication types will not have an input.
     static void onAuthAttempted(AuthType type, DOMString input);
   };
 };