Remove header dependencies from sequence_checker.h to sequenced_worker_pool.h

ios/chrome/browser/ui/omnibox/omnibox_popup_view_ios.mm

 // 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 "ios/chrome/browser/ui/omnibox/omnibox_popup_view_ios.h"
 
 #import <QuartzCore/QuartzCore.h>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/user_metrics.h"
 #include "base/metrics/user_metrics_action.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "components/omnibox/browser/autocomplete_match.h"
 #include "components/omnibox/browser/omnibox_edit_model.h"
 #include "components/omnibox/browser/omnibox_popup_model.h"
 #include "components/open_from_clipboard/clipboard_recent_content.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #import "ios/chrome/browser/experimental_flags.h"
 #import "ios/chrome/browser/ui/omnibox/omnibox_popup_material_view_controller.h"
 #import "ios/chrome/browser/ui/omnibox/omnibox_popup_positioner.h"
 #include "ios/chrome/browser/ui/omnibox/omnibox_util.h"
 #include "ios/chrome/browser/ui/omnibox/omnibox_view_ios.h"
@@ skipping 267 matching lines @@
     UMA_HISTOGRAM_LONG_TIMES_100(
         "MobileOmnibox.PressedClipboardSuggestionAge",
         ClipboardRecentContent::GetInstance()->GetClipboardContentAge());
   }
   edit_view_->OpenMatch(match, disposition, GURL(), base::string16(), row);
 }
 
 bool OmniboxPopupViewIOS::IsOpen() const {
   return is_open_;
 }