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 33 matching lines @@
   onNumberTap_: function(event, detail) {
     var numberValue = event.target.getAttribute('value');
     this.value += numberValue;
   },
 
   /** Fires a submit event with the current PIN value. */
   firePinSubmitEvent_: function() {
     this.fire('submit', { pin: this.value });
   },
 
+  /** Changes the color of the submit button if PIN is ready. */
+  changeSubmitColor_: function(pinLength) {
+    var button = this.querySelectorAll('.submit-button .icon-container')[0];
+    button.classList.toggle('ready-background', pinLength > 0);
+  },
+
   /**
    * Fires an update event with the current PIN value. The event will only be
    * fired if the PIN value has actually changed.
    * @param {string} value
    * @param {string} previous
    */
   onPinValueChange_: function(value, previous) {
-    if (value != previous)
+    if (value != previous) {
       this.fire('pin-change', { pin: value });
+      this.changeSubmitColor_(value.length);

[jdufault, 2016/06/27 19:17:52]

The color should only be blue if value.length > 0, right? If the user erases the
entire PIN it should go back to normal color.

+    }
   },
 
   /** Called when the user wants to erase the last character of the entered
    *  PIN value.
    */
   onPinClear_: function() {
     this.value = this.value.substring(0, this.value.length - 1);
   },
 
   /** Called when a key event is pressed while the input element has focus. */
   onInputKeyDown_: function(event) {
     // Up/down pressed, swallow the event to prevent the input value from
     // being incremented or decremented.
     if (event.keyCode == 38 || event.keyCode == 40) {
       event.preventDefault();
       return;
     }
 
     // Enter pressed.
     if (event.keyCode == 13) {
       this.firePinSubmitEvent_();
       event.preventDefault();
       return;
     }
   }
 });