Pin keyboard matches red lines (go/cros-quick-unlock-ux).

chrome/browser/resources/chromeos/quick_unlock/pin_keyboard.js

 // Copyright 2016 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.
 
 /**
  * @fileoverview
  * 'pin-keyboard' is a keyboard that can be used to enter PINs or more generally
  * numeric values.
  *
  * Properties:
@@ skipping 66 matching lines @@
       event.preventDefault();
       return;
     }
 
     // Enter pressed.
     if (event.keyCode == 13) {
       this.firePinSubmitEvent_();
       event.preventDefault();
       return;
     }
+  },
+
+  /**
+   * Changes the color of the submit button if PIN is ready.
+   * @param {string} value
+   */
+  computeSubmitClass_: function(value) {
+    return value.length > 0 ? 'ready-background' : '';
   }
 });