Override SigninManager::SignOut if force-signin is enabled.

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

 // Copyright 2015 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
  * 'settings-people-page' is the settings page containing sign-in settings.
  */
 Polymer({
   is: 'settings-people-page',
@@ skipping 229 matching lines @@
 
   /** @private */
   onDisconnectCancel_: function() {
     this.$.disconnectDialog.close();
   },
 
   /** @private */
   onDisconnectConfirm_: function() {
     var deleteProfile = !!this.syncStatus.domain ||
         (this.$.deleteProfile && this.$.deleteProfile.checked);
-    this.syncBrowserProxy_.signOut(deleteProfile);
-
-    this.$.disconnectDialog.close();
+    // Navigate to previous route before signout so session restore does
+    // not restore to the signout dialog. Dialog will be automatically
+    // closed by the route change.
+    settings.navigateToPreviousRoute();
+    setTimeout(function() {

[tommycli, 2016/11/01 17:28:54]

Thinking further on this: I think using setTimeout here is wrong. We have to
wait until the browse has finished its Back navigation.

So the right thing to do would be:

window.addEventListener('popstate', function callback() {
  window.removeEventListener('popstate', callback);
  this.syncBrowserProxy_.signOut(deleteProfile);
}.bind(this));

See if that fixes your tests too.

[Dan Beam, 2016/11/01 18:51:38]

see also: listenOnce()

+       this.syncBrowserProxy_.signOut(deleteProfile);
+    }.bind(this));
   },
 
   /** @private */
   onSyncTap_: function() {
     assert(this.syncStatus.signedIn);
     assert(this.syncStatus.syncSystemEnabled);
 
     if (this.syncStatus.managed)
       return;
 
@@ skipping 98 matching lines @@
 
   /**
    * @param {!settings.SyncStatus} syncStatus
    * @return {boolean} Whether to show the "Sign in to Chrome" button.
    * @private
    */
   showSignin_: function(syncStatus) {
     return !!syncStatus.signinAllowed && !syncStatus.signedIn;
   },
 });