Settings: Fix some BrowserProxy compile issues.

chrome/browser/resources/settings/people_page/sync_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.
 
 (function() {
 
 /**
  * Names of the radio buttons which allow the user to choose his encryption
  * mechanism.
  * @enum {string}
@@ skipping 60 matching lines @@
     /**
      * The current active route.
      */
     currentRoute: {
       type: Object,
       observer: 'currentRouteChanged_',
     },
 
     /**
      * The current sync preferences, supplied by SyncBrowserProxy.
      * @type {?settings.SyncPrefs}

[dschuyler, 2016/06/30 22:26:33]

Is it workable to set the type here to
  {!settings.SyncPrefs}
instead of doing the
    if (!this.syncPrefs)
below?

[tommycli, 2016/06/30 22:32:51]

No, because it's genuinely undefined until it's initialized by the c++ handler.

However, i did change this to an assert, since this can never reasonably happen.
That might be cleaner.

[Dan Beam, 2016/06/30 23:38:00]

fyi: ?Type means Type|null

This seems like Type|undefined as it doesn't explicitly set the initial value:
null

[tommycli, 2016/06/30 23:51:18]

Done.

      */
     syncPrefs: {
       type: Object,
     },
 
     /**
      * Caches the individually selected synced data types. This is used to
      * be able to restore the selections after checking and unchecking Sync All.
      * @private
      */
     cachedSyncPrefs_: {
       type: Object,
     },
 
     /**
      * Whether the "create passphrase" inputs should be shown. These inputs
      * give the user the opportunity to use a custom passphrase instead of
      * authenticating with his Google credentials.
      * @private
      */
     creatingNewPassphrase_: {
       type: Boolean,
       value: false,
     },
 
-    /** @private {!settings.SyncBrowserProxyImpl} */
+    /** @private {!settings.SyncBrowserProxy} */
     browserProxy_: {
       type: Object,
       value: function() {
         return settings.SyncBrowserProxyImpl.getInstance();
       },
     },
 
     /**
      * The unload callback is needed because the sign-in flow needs to know
      * if the user has closed the tab with the sync settings. This property is
@@ skipping 116 matching lines @@
     }
 
     this.onSingleSyncDataTypeChanged_();
   },
 
   /**
    * Handler for when any sync data type checkbox is changed (except autofill).
    * @private
    */
   onSingleSyncDataTypeChanged_: function() {
+    if (!this.syncPrefs)
+      return;
     this.browserProxy_.setSyncDatatypes(this.syncPrefs).then(
         this.handlePageStatusChanged_.bind(this));
   },
 
   /** @private */
   onManageSyncedDataTap_: function() {
     window.open(loadTimeData.getString('syncDashboardUrl'));
   },
 
   /**
@@ skipping 142 matching lines @@
 
     passphraseInput.invalid = emptyPassphrase;
     passphraseConfirmationInput.invalid =
         !emptyPassphrase && mismatchedPassphrase;
 
     return !emptyPassphrase && !mismatchedPassphrase;
   },
 });
 
 })();