Make using WebContentsUserData simpler.

chrome/browser/printing/print_preview_message_handler.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/printing/print_preview_message_handler.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/memory/ref_counted.h"
@@ skipping 10 matching lines @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_ui.h"
 #include "printing/page_size_margins.h"
 #include "printing/print_job_constants.h"
 
 using content::BrowserThread;
 using content::WebContents;
 
-int printing::PrintPreviewMessageHandler::kUserDataKey;
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(printing::PrintPreviewMessageHandler)
 
 namespace {
 
 void StopWorker(int document_cookie) {
   if (document_cookie <= 0)
     return;
 
   printing::PrintJobManager* print_job_manager =
       g_browser_process->print_job_manager();
   scoped_refptr<printing::PrinterQuery> printer_query;
@@ skipping 200 matching lines @@
     IPC_MESSAGE_HANDLER(PrintHostMsg_PrintPreviewInvalidPrinterSettings,
                         OnInvalidPrinterSettings)
     IPC_MESSAGE_HANDLER(PrintHostMsg_PrintPreviewScalingDisabled,
                         OnPrintPreviewScalingDisabled)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
 }
 
 }  // namespace printing