Settings People Revamp: Cache the selected Sync individual data types.

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 49 matching lines @@
 
     /**
      * The current sync preferences, supplied by SyncBrowserProxy.
      * @type {?settings.SyncPrefs}
      */
     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.

[dpapad, 2016/06/28 22:23:32]

@private

[tommycli, 2016/06/29 00:04:07]

Done.

+     */
+    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,
     },
 
@@ skipping 101 matching lines @@
     if (this.syncPrefs.encryptAllData)
       this.creatingNewPassphrase_ = false;
   },
 
   /**
    * Handler for when the sync all data types checkbox is changed.
    * @param {Event} event
    * @private
    */
   onSyncAllDataTypesChanged_: function(event) {
+    var SyncPrefsIndividualDataTypes = [

[dpapad, 2016/06/28 22:23:33]

Can this array be moved outside this function as a local constant to the
surrounding function scope? Seems unnecessary to redefine this array every time
onSyncAllataTypesChanged_ executes.

[tommycli, 2016/06/29 00:04:07]

Done.

+      'appsSynced',
+      'extensionsSynced',
+      'preferencesSynced',
+      'autofillSynced',
+      'typedUrlsSynced',
+      'themesSynced',
+      'bookmarksSynced',
+      'passwordsSynced',
+      'tabsSynced',
+      'paymentsIntegrationEnabled',
+    ];
+
     if (event.target.checked) {
       this.set('syncPrefs.syncAllDataTypes', true);
-      this.set('syncPrefs.appsSynced', true);
-      this.set('syncPrefs.extensionsSynced', true);
-      this.set('syncPrefs.preferencesSynced', true);
-      this.set('syncPrefs.autofillSynced', true);
-      this.set('syncPrefs.typedUrlsSynced', true);
-      this.set('syncPrefs.themesSynced', true);
-      this.set('syncPrefs.bookmarksSynced', true);
-      this.set('syncPrefs.passwordsSynced', true);
-      this.set('syncPrefs.tabsSynced', true);
-      this.set('syncPrefs.paymentsIntegrationEnabled', true);
+
+      // Cache the previously selected preference before checking every box.
+      this.cachedSyncPrefs_ = {};
+      for (dataType of SyncPrefsIndividualDataTypes) {
+        this.cachedSyncPrefs_[dataType] = this.syncPrefs[dataType];

[dpapad, 2016/06/28 22:23:33]

What is the key/value pair of syncPrefs look like? Is this shallow copy
sufficient? If some of the values are complex objects themselves, then the
cachedSyncPrefs and syncPrefs will hold references to the exact same object. If
all values are primitives, then let's add a comment explaining that the shallow
copy to store prefs is good enough.

[tommycli, 2016/06/29 00:04:07]

Done. I added a comment.

+
+        this.set(['syncPrefs', dataType], true);
+      }
+    } else if (this.cachedSyncPrefs_) {
+      // Restore the previously selected preference.
+      for (dataType of SyncPrefsIndividualDataTypes) {
+        this.set(['syncPrefs', dataType], this.cachedSyncPrefs_[dataType]);
+      }
     }
 
     this.onSingleSyncDataTypeChanged_();
   },
 
   /**
    * Handler for when any sync data type checkbox is changed (except autofill).
    * @private
    */
   onSingleSyncDataTypeChanged_: function() {
@@ skipping 152 matching lines @@
 
     passphraseInput.invalid = emptyPassphrase;
     passphraseConfirmationInput.invalid =
         !emptyPassphrase && mismatchedPassphrase;
 
     return !emptyPassphrase && !mismatchedPassphrase;
   },
 });
 
 })();