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 ca343b2e90386434eff0b825f3037bc075960652..5d926c40bab7d1f345c0c8faae172d304cb7656e 100644
--- a/chrome/browser/resources/chromeos/quick_unlock/pin_keyboard.js
+++ b/chrome/browser/resources/chromeos/quick_unlock/pin_keyboard.js
@@ -35,15 +35,32 @@ Polymer({
     }
   },
 
+  // The current focused element.
+  focusedElement_: undefined,
+
   /** Transfers focus to the input element. */
   focus: function() {
-    this.$$('#pin-input').focus();
+    var pinInput = this.$$('#pin-input');
+    pinInput.focus();
+    this.focusedElement_ = pinInput;
+  },
+
+  /** Called when a pin keyboard has a key pressed. */
+  onButtonKeyUp_: function(event, detail) {
+    // Only if tab has been pressed do we want change the focus.
+    if (event.target.receivedFocusFromKeyboard)
+      this.focusedElement_ = event.target;
   },
 
   /** Called when a keypad number has been tapped. */
   onNumberTap_: function(event, detail) {
     var numberValue = event.target.getAttribute('value');
     this.value += numberValue;
+
+    // If the tabbed element is clicked we want to keep the focus, otherwise
+    // transfer focus to the input.
+    if (this.focusedElement_ != event.target)
+      this.focus();

[jdufault, 2016/07/06 19:07:05]

Can this just be

  // Only focus buttons if the user tabbed to them.
  if (!event.target.receivedFocusFromKeyboard)
    this.focus()

If that works, then all the other changes can be reverted.

   },
 
   /** Fires a submit event with the current PIN value. */