Hide other users row when there is no other user on the current device

Before this change, when there's a single user on a device, the storage
handler immediately returns '0 B' as the "Other users" size.

This change hides the "Other users" row entirely on the storage page
instead.

Test: browser_tests --gtest_filter="*OSSettingsDevicePageTest.StorageTest"
Bug: 1056491
Change-Id: Ibbc587ff702c5cc419eab35e7c0129674a9f9897
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2076747Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Jeremie Boulic <jboulic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745645}

chrome/browser/resources/settings/chromeos/device_page/storage.html

@@ -220,7 +220,7 @@
           role-description="$i18n{subpageArrowRoleDescription}">
       </cr-link-row>
     </template>
-    <template is="dom-if" if="[[!isGuest_]]">
+    <template is="dom-if" if="[[showOtherUsers_]]">
       <cr-link-row id="otherUsersSize" class="hr" on-click="onOtherUsersTap_"
           label="$i18n{storageItemOtherUsers}"
           sub-label="$i18n{storageSizeComputing}"

chrome/browser/resources/settings/chromeos/device_page/storage.js

@@ -53,6 +53,15 @@ Polymer({
       }
     },
 
+    /** @private */
+    showOtherUsers_: {
+      type: Boolean,
+      // Initialize showOtherUsers_ to false if the user is in guest mode.
+      value() {
+        return !loadTimeData.getBoolean('isGuest');
+      }
+    },
+
     /** @private {settings.StorageSizeStat} */
     sizeStat_: Object,
   },
@@ -227,12 +236,17 @@ Polymer({
 
   /**
    * @param {string} size Formatted string representing the size of Other users.
+   * @param {boolean} noOtherUsers True if there is no other registered users on
+   *     the device.
    * @private
    */
-  handleOtherUsersSizeChanged_(size) {
-    if (!this.isGuest_) {
-      this.$$('#otherUsersSize').subLabel = size;
+  handleOtherUsersSizeChanged_(size, noOtherUsers) {
+    if (this.isGuest_ || noOtherUsers) {
+      this.showOtherUsers_ = false;
+      return;
     }
+    this.showOtherUsers_ = true;
+    this.$$('#otherUsersSize').subLabel = size;
   },
 
   /**

chrome/browser/ui/webui/settings/chromeos/device_storage_handler.cc

@@ -223,7 +223,13 @@ void StorageHandler::UpdateStorageItem(const std::string& event_name,
     message = ui::FormatBytes(total_bytes);
   }
 
-  FireWebUIListener(event_name, base::Value(message));
+  if (event_name == "storage-other-users-size-changed") {
+    bool no_other_users = (total_bytes == 0);
+    FireWebUIListener(event_name, base::Value(message),
+                      base::Value(no_other_users));
+  } else {
+    FireWebUIListener(event_name, base::Value(message));
+  }
 }
 
 void StorageHandler::UpdateSizeStat(const std::string& event_name,

chrome/test/data/webui/settings/chromeos/device_page_tests.js

@@ -1934,6 +1934,36 @@ cr.define('device_page_tests', function() {
         Polymer.dom.flush();
         assertEquals('59.5 KB', getStorageItemSubLabelFromId('appsSize'));
       });
+
+      test('other users size', async function() {
+        // The other users row is visible by default, displaying
+        // "calculating...".
+        assertFalse(isHidden(storagePage.$$('#otherUsersSize')));
+        assertEquals(
+            'Other users', getStorageItemLabelFromId('otherUsersSize'));
+        assertEquals(
+            'Calculating…', getStorageItemSubLabelFromId('otherUsersSize'));
+
+        // Simulate absence of other users.
+        cr.webUIListenerCallback(
+            'storage-other-users-size-changed', '0 B', true);
+        Polymer.dom.flush();
+        assertTrue(isHidden(storagePage.$$('#otherUsersSize')));
+
+        // Send other users callback with a size that is not null.
+        cr.webUIListenerCallback(
+            'storage-other-users-size-changed', '322 MB', false);
+        Polymer.dom.flush();
+        assertFalse(isHidden(storagePage.$$('#otherUsersSize')));
+        assertEquals('322 MB', getStorageItemSubLabelFromId('otherUsersSize'));
+
+        // If the user is in Guest mode, the row is not visible.
+        storagePage.isGuest_ = true;
+        cr.webUIListenerCallback(
+            'storage-other-users-size-changed', '322 MB', false);
+        Polymer.dom.flush();
+        assertTrue(isHidden(storagePage.$$('#otherUsersSize')));
+      });
     });
   });