settings: Prevent use enter when next button disabled on set up PIN.

Also add a tooltip to PIN keyboard back button.

Test: manual
Bug: 848681, 845871
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ic1ba4e80ee2386ffe587ffd4bc791a29548e7254
Reviewed-on: https://chromium-review.googlesource.com/1095649Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567394}

chrome/browser/resources/settings/people_page/setup_pin_dialog.js

@@ -274,6 +274,8 @@ Polymer({
   /** @private */
   onPinSubmit_: function() {
     if (!this.isConfirmStep_) {
+      if (!this.enableSubmit_)
+        return;
       this.initialPin_ = this.pinKeyboardValue_;
       this.pinKeyboardValue_ = '';
       this.isConfirmStep_ = true;

ui/webui/resources/cr_components/chromeos/quick_unlock/pin_keyboard.html

@@ -254,7 +254,7 @@
               on-pointerdown="onBackspacePointerDown_"
               on-pointerout="clearAndReset_"
               on-pointerup="onBackspacePointerUp_"
-              aria-label="[[i18n('pinKeyboardDeleteAccessibleName')]]"
+              title="[[i18n('pinKeyboardDeleteAccessibleName')]]"
               noink>
           </paper-icon-button>
           <paper-ripple>