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

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

Index: chrome/browser/resources/chromeos/quick_unlock/pin_keyboard.js
diff --git a/chrome/browser/resources/chromeos/quick_unlock/pin_keyboard.js b/chrome/browser/resources/chromeos/quick_unlock/pin_keyboard.js
index de93c08df1b17741ac5612be76bb7a37cf141619..85c404a1489532a4686a465d6f3db3b3eca660bb 100644
--- a/chrome/browser/resources/chromeos/quick_unlock/pin_keyboard.js
+++ b/chrome/browser/resources/chromeos/quick_unlock/pin_keyboard.js
@@ -53,10 +53,21 @@ Polymer({
     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. */