Remove last dependency of HistoryService on //content

chrome/browser/history/history_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.
 
 // The history system runs on a background thread so that potentially slow
 // database operations don't delay the browser. This backend processing is
 // represented by HistoryBackend. The HistoryService's job is to dispatch to
 // that thread.
 //
 // Main thread                       History thread
@@ skipping 723 matching lines @@
   DCHECK(thread_) << "History service being called after cleanup";
   DCHECK(thread_checker_.CalledOnValidThread());
   PostTaskAndReplyWithResult(
       thread_->message_loop_proxy().get(),
       FROM_HERE,
       base::Bind(
           &HistoryBackend::CreateDownload, history_backend_.get(), create_info),
       callback);
 }
 
-void HistoryService::GetNextDownloadId(
-    const content::DownloadIdCallback& callback) {
+void HistoryService::GetNextDownloadId(const DownloadIdCallback& callback) {
   DCHECK(thread_) << "History service being called after cleanup";
   DCHECK(thread_checker_.CalledOnValidThread());
   PostTaskAndReplyWithResult(
       thread_->message_loop_proxy().get(),
       FROM_HERE,
       base::Bind(&HistoryBackend::GetNextDownloadId, history_backend_.get()),
       callback);
 }
 
 // Handle queries for a list of all downloads in the history database's
@@ skipping 537 matching lines @@
     const HistoryService::OnFaviconChangedCallback& callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
   return favicon_changed_callback_list_.Add(callback);
 }
 
 void HistoryService::NotifyFaviconChanged(
     const std::set<GURL>& changed_favicons) {
   DCHECK(thread_checker_.CalledOnValidThread());
   favicon_changed_callback_list_.Notify(changed_favicons);
 }