Convert RLZ to a buildflag header

chrome/browser/extensions/api/music_manager_private/device_id_win.cc

 // Copyright 2013 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/extensions/api/music_manager_private/device_id.h"
 
 // Note: The order of header includes is important, as we want both pre-Vista
 // and post-Vista data structures to be defined, specifically
 // PIP_ADAPTER_ADDRESSES and PMIB_IF_ROW2.
 
 #include <limits.h>
 #include <stddef.h>
 #include <winsock2.h>
 #include <ws2def.h>
 #include <ws2ipdef.h>
 #include <iphlpapi.h>
 
 #include <string>
 
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/scoped_native_library.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/win/windows_version.h"
 #include "content/public/browser/browser_thread.h"
+#include "rlz/features/features.h"
 
-#if defined(ENABLE_RLZ)
+#if BUILDFLAG(ENABLE_RLZ)
 #include "rlz/lib/machine_id.h"
 #endif
 
 namespace {
 
 using extensions::api::DeviceId;
 
 typedef base::Callback<bool(const void* bytes, size_t size)>
     IsValidMacAddressCallback;
 
@@ skipping 136 matching lines @@
     LOG(ERROR) << "Could not find appropriate MAC address.";
   }
 
   content::BrowserThread::PostTask(
       content::BrowserThread::UI,
       FROM_HERE,
       base::Bind(callback, mac_address));
 }
 
 std::string GetRlzMachineId() {
-#if defined(ENABLE_RLZ)
+#if BUILDFLAG(ENABLE_RLZ)
   std::string machine_id;
   if (!rlz_lib::GetMachineId(&machine_id))
-    return "";
+    return std::string();
   return machine_id;
 #else
-  return "";
+  return std::string();
 #endif
 }
 
 void GetMacAddressCallback(const DeviceId::IdCallback& callback,
                            const std::string& mac_address) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
   std::string machine_id = GetRlzMachineId();
   if (mac_address.empty() || machine_id.empty()) {
     callback.Run("");
@@ skipping 14 matching lines @@
   content::BrowserThread::PostTask(
       content::BrowserThread::FILE,
       FROM_HERE,
       base::Bind(GetMacAddress,
         base::Bind(DeviceId::IsValidMacAddress),
         base::Bind(GetMacAddressCallback, callback)));
 }
 
 }  // namespace api
 }  // namespace extensions