Smart Lock: Adjust settings to work with Polymer 2.

The |authToken_| property needed to be explicitly bound.

Bug: 933974
Change-Id: I7b0ec1d2d4750460f437137f8441ff1413a3345d
Reviewed-on: https://chromium-review.googlesource.com/c/1481090Reviewed-by: Jeremy Klein <jlklein@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634457}

chrome/browser/resources/settings/multidevice_page/multidevice_page.html

@@ -110,7 +110,8 @@
       </template>
     </settings-animated-pages>
     <template is="dom-if" if="[[showPasswordPromptDialog_]]" restamp>
-      <settings-password-prompt-dialog id="multidevicePasswordPrompt">
+      <settings-password-prompt-dialog id="multidevicePasswordPrompt"
+          auth-token="{{authToken_}}">
       </settings-password-prompt-dialog>
     </template>
   </template>

chrome/test/data/webui/settings/multidevice_page_tests.js

@@ -59,7 +59,8 @@ suite('Multidevice', function() {
     if (authRequired) {
       assertTrue(multidevicePage.showPasswordPromptDialog_);
       // Simulate the user entering a valid password, then closing the dialog.
-      multidevicePage.fire('auth-token-changed', {value: 'validAuthToken'});
+      multidevicePage.$$('#multidevicePasswordPrompt').authToken =
+          'validAuthToken';
       // Simulate closing the password prompt dialog
       multidevicePage.$$('#multidevicePasswordPrompt').fire('close');
       Polymer.dom.flush();