Pin keyboard use enter to submit when focus is not on a button.

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 35 matching lines @@
       value: '',
       observer: 'onPinValueChange_'
     }
   },
 
   /** Transfers focus to the input element. */
   focus: function() {
     this.$$('#pin-input').focus();
   },
 
-  /** Called when a keypad number has been tapped. */
+  /**
+   * Called when a keypad number has been tapped.
+   * @param {!{target: !PaperButtonElement}} event
+   * @private
+   */
   onNumberTap_: function(event, detail) {
     var numberValue = event.target.getAttribute('value');
     this.value += numberValue;
+
+    // If a number button is clicked, we do not want to switch focus to the
+    // button, therefore we transfer focus back to the input, but if a number
+    // button is tabbed into, it should keep focus, so users can use tab and
+    // spacebar/return to enter their PIN.
+    if (!event.target.receivedFocusFromKeyboard)
+      this.focus();
   },
 
   /** Fires a submit event with the current PIN value. */
   firePinSubmitEvent_: function() {
     this.fire('submit', { pin: this.value });
   },
 
   /**
    * Fires an update event with the current PIN value. The event will only be
    * fired if the PIN value has actually changed.
@@ skipping 65 matching lines @@
     // does not contain decimals.
     // This heuristic will fail for inputs like '1.0'.
     //
     // Since we still support users entering their passwords through the PIN
     // keyboard, we swap the input box to rtl when we think it is a password
     // (just numbers), if the document direction is rtl.
     var enableRtl = (document.dir == 'rtl') && !Number.isInteger(+password);
     return enableRtl ? 'input-non-pin' : '';
   }
 });