Switch browser/extensions/api/file_system/file_system_api.[h|cc] to the TaskScheduler API

chrome/browser/extensions/api/file_system/file_system_api.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_FILE_SYSTEM_FILE_SYSTEM_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_FILE_SYSTEM_FILE_SYSTEM_API_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/task_scheduler/post_task.h"
 #include "base/values.h"
 #include "build/build_config.h"
 #include "chrome/browser/extensions/chrome_extension_function.h"
 #include "chrome/browser/extensions/chrome_extension_function_details.h"
 #include "chrome/common/extensions/api/file_system.h"
 #include "extensions/browser/extension_function.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/shell_dialogs/select_file_dialog.h"
 
 #if defined(OS_CHROMEOS)
@@ skipping 124 matching lines @@
 
  protected:
   ~FileSystemGetDisplayPathFunction() override {}
   ResponseAction Run() override;
 };
 
 class FileSystemEntryFunction : public ChromeAsyncExtensionFunction {
  protected:
   FileSystemEntryFunction();
 
-  ~FileSystemEntryFunction() override {}
+  ~FileSystemEntryFunction() override;
 
   // This is called when writable file entries are being returned. The function
   // will ensure the files exist, creating them if necessary, and also check
   // that none of the files are links. If it succeeds it proceeds to
   // RegisterFileSystemsAndSendResponse, otherwise to HandleWritableFileError.
   void PrepareFilesForWritableApp(const std::vector<base::FilePath>& path);
 
   // This will finish the choose file process. This is either called directly
   // from FilesSelected, or from WritableFileChecker. It is called on the UI
   // thread.
   void RegisterFileSystemsAndSendResponse(
       const std::vector<base::FilePath>& path);
 
   // Creates a result dictionary.
   std::unique_ptr<base::DictionaryValue> CreateResult();
 
   // Adds an entry to the result dictionary.
   void AddEntryToResult(const base::FilePath& path,
                         const std::string& id_override,
                         base::DictionaryValue* result);
 
   // called on the UI thread if there is a problem checking a writable file.
   void HandleWritableFileError(const base::FilePath& error_path);
 
   // Whether multiple entries have been requested.
   bool multiple_;
 
   // Whether a directory has been requested.
   bool is_directory_;
+
+  // The task runner used to do file operations.
+  const scoped_refptr<base::SequencedTaskRunner> task_runner_ =
+      base::CreateSequencedTaskRunnerWithTraits(
+          {base::MayBlock(), base::TaskPriority::BACKGROUND});
 };
 
 class FileSystemGetWritableEntryFunction : public FileSystemEntryFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("fileSystem.getWritableEntry",
                              FILESYSTEM_GETWRITABLEENTRY)
 
  protected:
   ~FileSystemGetWritableEntryFunction() override {}
   bool RunAsync() override;
@@ skipping 212 matching lines @@
   ExtensionFunction::ResponseAction Run() override;
 
  private:
   ChromeExtensionFunctionDetails chrome_details_;
 };
 #endif
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_FILE_SYSTEM_FILE_SYSTEM_API_H_