cros: Clean up screenlockPrivate plumbing.

chrome/common/extensions/api/screenlock_private.idl

Index: chrome/common/extensions/api/screenlock_private.idl
diff --git a/chrome/common/extensions/api/screenlock_private.idl b/chrome/common/extensions/api/screenlock_private.idl
index 2fecef7ba29fef62b7508697bd5f3e9669cb585e..36ebc7685e930861d5da6184bdf3ba1723bdd89a 100644
--- a/chrome/common/extensions/api/screenlock_private.idl
+++ b/chrome/common/extensions/api/screenlock_private.idl
@@ -30,12 +30,12 @@ namespace screenlockPrivate {
     // 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);
@@ -54,9 +54,6 @@ namespace screenlockPrivate {
     // 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.