Use ENABLE_PRE_SYNC_BACKUP to disable test related to backup on iOS.

BUG=388506

Review URL: https://codereview.chromium.org/386093002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@282768 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/sync/profile_sync_service_unittest.cc

@@ -419,7 +419,7 @@ TEST_F(ProfileSyncServiceTest, DisableAndEnableSyncTemporarily) {
 
 // Certain ProfileSyncService tests don't apply to Chrome OS, for example
 // things that deal with concepts like "signing out" and policy.
-#if defined(OS_WIN) || defined(OS_MACOSX) || (defined(OS_LINUX) && !defined(OS_CHROMEOS))
+#if defined(ENABLE_PRE_SYNC_BACKUP)
 TEST_F(ProfileSyncServiceTest, EnableSyncAndSignOutDesktop) {
   CreateService(browser_sync::AUTO_START);
   ExpectDataTypeManagerCreation(2);