MD Settings: Put fingerprints on its own subpage.

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

 // Copyright 2016 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-lock-screen' allows the user to change how they unlock their
  * device.
  *
  * Example:
@@ skipping 65 matching lines @@
   },
 
   /** selectedUnlockType is defined in LockStateBehavior. */
   observers: ['selectedUnlockTypeChanged_(selectedUnlockType)'],
 
   /** @override */
   attached: function() {
     // currentRouteChanged is not called during the initial navigation. If the
     // user navigates directly to the lockScreen page, we still want to show the
     // password prompt page.
-    this.currentRouteChanged();
+    this.currentRouteChanged(settings.Route.LOCK_SCREEN,
+        settings.Route.LOCK_SCREEN);
   },
 
   /**
    * Overridden from settings.RouteObserverBehavior.
+   * @param {!settings.Route} newRoute
+   * @param {!settings.Route} oldRoute
    * @protected
    */
-  currentRouteChanged: function() {
-    if (settings.getCurrentRoute() == settings.Route.LOCK_SCREEN &&
-        !this.setModes_) {
+  currentRouteChanged: function(newRoute, oldRoute) {
+    if (newRoute == settings.Route.LOCK_SCREEN && !this.setModes_) {
       this.$.passwordPrompt.open();
-    } else {
+    } else if (newRoute != settings.Route.FINGERPRINT &&
+        oldRoute != settings.Route.FINGERPRINT) {
       // If the user navigated away from the lock screen settings page they will
-      // have to re-enter their password.
+      // have to re-enter their password. An exception is if they are navigating
+      // to or from the fingerprint subpage.
       this.setModes_ = undefined;
     }
   },
 
   /**
    * Called when the unlock type has changed.
    * @param {!string} selected The current unlock type.
    * @private
    */
   selectedUnlockTypeChanged_: function(selected) {
@@ skipping 46 matching lines @@
 
   /**
    * @param {!Event} e
    * @private
    */
   onConfigurePin_: function(e) {
     e.preventDefault();
     this.$.setupPin.open();
     this.writeUma_(LockScreenProgress.CHOOSE_PIN_OR_PASSWORD);
   },
+
+  /** @private */
+  onEditFingerprints_: function() {
+    settings.navigateTo(settings.Route.FINGERPRINT);
+  },
 });