Cleanup: Use PostTaskAndReplyWithResults instead of passing callbacks around in downloads code.

chrome/browser/download/chrome_download_manager_delegate.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/download/chrome_download_manager_delegate.h"
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/file_util.h"
 #include "base/prefs/pref_member.h"
 #include "base/prefs/pref_service.h"
 #include "base/rand_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/task_runner.h"
+#include "base/task_runner_util.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "base/time/time.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/download/download_completion_blocker.h"
 #include "chrome/browser/download/download_crx_util.h"
 #include "chrome/browser/download/download_file_picker.h"
 #include "chrome/browser/download/download_history.h"
 #include "chrome/browser/download/download_item_model.h"
 #include "chrome/browser/download/download_path_reservation_tracker.h"
@@ skipping 140 matching lines @@
     // If the URL is malicious, we'll use that as the danger type. The results
     // of the content check, if one is performed, will be ignored.
     danger_type = content::DOWNLOAD_DANGER_TYPE_DANGEROUS_URL;
   }
   callback.Run(danger_type);
 }
 
 #endif  // FULL_SAFE_BROWSING
 
 // Called on the blocking pool to determine the MIME type for |path|.
-void GetMimeTypeAndReplyOnUIThread(
-    const base::FilePath& path,
-    const base::Callback<void(const std::string&)>& callback) {
+std::string GetMimeType(const base::FilePath& path) {
   std::string mime_type;
   net::GetMimeTypeFromFile(path, &mime_type);
-  BrowserThread::PostTask(
-      BrowserThread::UI, FROM_HERE, base::Bind(callback, mime_type));
+  return mime_type;
 }
 
 bool IsOpenInBrowserPreferreredForFile(const base::FilePath& path) {
   // On Android, always prefer opening with an external app. On ChromeOS, there
   // are no external apps so just allow all opens to be handled by the "System."
 #if !defined(OS_ANDROID) && !defined(OS_CHROMEOS) && defined(ENABLE_PLUGINS)
   // TODO(asanka): Consider other file types and MIME types.
   // http://crbug.com/323561
   if (path.MatchesExtension(FILE_PATH_LITERAL(".pdf")) ||
       path.MatchesExtension(FILE_PATH_LITERAL(".htm")) ||
@@ skipping 432 matching lines @@
                                          is_content_check_supported));
     return;
   }
 #endif
   callback.Run(content::DOWNLOAD_DANGER_TYPE_NOT_DANGEROUS);
 }
 
 void ChromeDownloadManagerDelegate::GetFileMimeType(
     const base::FilePath& path,
     const GetFileMimeTypeCallback& callback) {
-  BrowserThread::PostBlockingPoolTask(
-      FROM_HERE,
-      base::Bind(&GetMimeTypeAndReplyOnUIThread, path, callback));
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  base::PostTaskAndReplyWithResult(BrowserThread::GetBlockingPool(),
+                                   FROM_HERE,
+                                   base::Bind(&GetMimeType, path),
+                                   callback);
 }
 
 #if defined(FULL_SAFE_BROWSING)
 void ChromeDownloadManagerDelegate::CheckClientDownloadDone(
     uint32 download_id,
     DownloadProtectionService::DownloadCheckResult result) {
   DownloadItem* item = download_manager_->GetDownload(download_id);
   if (!item || (item->GetState() != DownloadItem::IN_PROGRESS))
     return;
 
@@ skipping 63 matching lines @@
   DownloadItem* item = download_manager_->GetDownload(download_id);
   if (!target_info->target_path.empty() && item &&
       IsOpenInBrowserPreferreredForFile(target_info->target_path) &&
       target_info->is_filetype_handled_safely)
     DownloadItemModel(item).SetShouldPreferOpeningInBrowser(true);
   callback.Run(target_info->target_path,
                target_info->target_disposition,
                target_info->danger_type,
                target_info->intermediate_path);
 }