Make DownloadItem derive SupportsUserData instead of re-implementing it.

chrome/browser/extensions/webstore_installer.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/extensions/webstore_installer.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/file_util.h"
@@ skipping 149 matching lines @@
   result->profile = profile;
   result->parsed_manifest = parsed_manifest.Pass();
   result->skip_install_dialog = true;
   return result.Pass();
 }
 
 WebstoreInstaller::Approval::~Approval() {}
 
 const WebstoreInstaller::Approval* WebstoreInstaller::GetAssociatedApproval(
     const DownloadItem& download) {
-  return static_cast<const Approval*>(download.GetExternalData(kApprovalKey));
+  return static_cast<const Approval*>(download.GetUserData(kApprovalKey));
 }
 
 WebstoreInstaller::WebstoreInstaller(Profile* profile,
                                      Delegate* delegate,
                                      NavigationController* controller,
                                      const std::string& id,
                                      scoped_ptr<Approval> approval,
                                      int flags)
     : profile_(profile),
       delegate_(delegate),
@@ skipping 94 matching lines @@
     return;
   }
 
   CHECK(id.IsValid());
 
   DownloadManager* download_manager =
       BrowserContext::GetDownloadManager(profile_);
   download_item_ = download_manager->GetActiveDownloadItem(id.local());
   download_item_->AddObserver(this);
   if (approval_.get())
-    download_item_->SetExternalData(kApprovalKey, approval_.release());
+    download_item_->SetUserData(kApprovalKey, approval_.release());
 }
 
 void WebstoreInstaller::OnDownloadUpdated(DownloadItem* download) {
   CHECK_EQ(download_item_, download);
 
   switch (download->GetState()) {
     case DownloadItem::CANCELLED:
       ReportFailure(kDownloadCanceledError);
       break;
     case DownloadItem::INTERRUPTED:
@@ skipping 57 matching lines @@
 void WebstoreInstaller::ReportSuccess() {
   if (delegate_) {
     delegate_->OnExtensionInstallSuccess(id_);
     delegate_ = NULL;
   }
 
   Release();  // Balanced in Start().
 }
 
 }  // namespace extensions