Use TaskScheduler instead of WorkerPool in extension_printer_handler.cc.

chrome/browser/ui/webui/print_preview/extension_printer_handler.h

 // Copyright 2015 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_EXTENSION_PRINTER_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_EXTENSION_PRINTER_HANDLER_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/strings/string16.h"
 #include "chrome/browser/ui/webui/print_preview/printer_handler.h"
 #include "extensions/browser/api/printer_provider/printer_provider_api.h"
 
 namespace base {
 class DictionaryValue;
 class ListValue;
 class RefCountedMemory;
-class TaskRunner;
 }
 
 namespace content {
 class BrowserContext;
 }
 
 namespace cloud_devices {
 class CloudDeviceDescription;
 }
 
 namespace device {
 class UsbDevice;
 }
 
 namespace gfx {
 class Size;
 }
 
 namespace printing {
 class PWGRasterConverter;
 }
 
 // Implementation of PrinterHandler interface backed by printerProvider
 // extension API.
 class ExtensionPrinterHandler : public PrinterHandler {
  public:
   using PrintJobCallback = base::Callback<void(
       std::unique_ptr<extensions::PrinterProviderPrintJob>)>;
 
-  ExtensionPrinterHandler(
-      content::BrowserContext* browser_context,
-      const scoped_refptr<base::TaskRunner>& slow_task_runner);
+  explicit ExtensionPrinterHandler(content::BrowserContext* browser_context);
 
   ~ExtensionPrinterHandler() override;
 
   // PrinterHandler implementation:
   void Reset() override;
   void StartGetPrinters(
       const PrinterHandler::GetPrintersCallback& callback) override;
   void StartGetCapability(
       const std::string& destination_id,
       const PrinterHandler::GetCapabilityCallback& calback) override;
@@ skipping 50 matching lines @@
 
   void OnUsbDevicesEnumerated(
       const PrinterHandler::GetPrintersCallback& callback,
       const std::vector<scoped_refptr<device::UsbDevice>>& devices);
 
   content::BrowserContext* browser_context_;
 
   std::unique_ptr<printing::PWGRasterConverter> pwg_raster_converter_;
   int pending_enumeration_count_ = 0;
 
-  scoped_refptr<base::TaskRunner> slow_task_runner_;
-
   base::WeakPtrFactory<ExtensionPrinterHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionPrinterHandler);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_EXTENSION_PRINTER_HANDLER_H_