Define a single macro for enabling backup function.

chrome/browser/sync/profile_sync_service.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/sync/profile_sync_service.h"
 
 #include <cstddef>
 #include <map>
 #include <set>
 #include <utility>
@@ skipping 293 matching lines @@
       << "Initialize() called more than once.";
   sync_error_controller_.reset(new SyncErrorController(this));
   AddObserver(sync_error_controller_.get());
 #endif
 
   startup_controller_.Reset(GetRegisteredDataTypes());
   startup_controller_.TryStart();
 
   backup_rollback_controller_.Start(backup_start_delay_);
 
-#if defined(OS_WIN) || defined(OS_MACOSX) || (defined(OS_LINUX) && !defined(OS_CHROMEOS))
+#if defined(ENABLE_PRE_SYNC_BACKUP)
   if (CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kSyncDisableBackup)) {
     profile_->GetIOTaskRunner()->PostDelayedTask(
         FROM_HERE,
         base::Bind(base::IgnoreResult(base::DeleteFile),
                    profile_->GetPath().Append(kSyncBackupDataFolderName),
                    true),
         backup_start_delay_);
   }
 #endif
@@ skipping 2225 matching lines @@
       if (custom_sync_url.is_valid()) {
         result = custom_sync_url;
       } else {
         LOG(WARNING) << "The following sync URL specified at the command-line "
                      << "is invalid: " << value;
       }
     }
   }
   return result;
 }