gdata: Fix "save as pdf" to work on Google Drive.

chrome/browser/chromeos/gdata/file_write_helper.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_CHROMEOS_GDATA_FILE_WRITE_HELPER_H_
+#define CHROME_BROWSER_CHROMEOS_GDATA_FILE_WRITE_HELPER_H_
+
+#include "base/bind.h"
+#include "base/file_path.h"
+#include "base/memory/weak_ptr.h"
+#include "chrome/browser/chromeos/gdata/gdata_errorcode.h"
+#include "chrome/browser/chromeos/gdata/gdata_file_system_interface.h"
+
+namespace gdata {
+
+// This class provides higher level operations for writing to GData files over
+// GDataFileSystemInterface.
+class FileWriteHelper {
+ public:
+  explicit FileWriteHelper(GDataFileSystemInterface* file_system);
+  ~FileWriteHelper();
+
+  // Prepares a local temporary file path and passes it to |callback| on the
+  // blocking thread pool that allows file operations. The modification to
+  // the file is reflected to GData |path|. If |path| does not exist, a new
+  // file is created.
+  //
+  // Must be called from UI thread.
+  void PrepareWritableFileAndRun(const FilePath& path,
+                                 const OpenFileCallback& callback);
+
+ private:
+  // Part of PrepareWritableFilePathAndRun(). It tries CreateFile for the case
+  // file does not exist yet, does OpenFile to download and mark the file as
+  // dirty, runs |callback|, and finally calls CloseFile.
+  void PrepareWritableFileAndRunAfterCreateFile(
+      const FilePath& file_path,
+      const OpenFileCallback& callback,
+      GDataFileError result);
+  void PrepareWritableFileAndRunAfterOpenFile(
+      const FilePath& file_path,
+      const OpenFileCallback& callback,
+      GDataFileError result,
+      const FilePath& local_cache_path);
+  void PrepareWritableFileAndRunAfterCallback(const FilePath& file_path);
+
+  // File system owned by GDataSystemService.
+  GDataFileSystemInterface* file_system_;
+
+  // WeakPtrFactory bound to the UI thread.
+  // Note: This should remain the last member so it'll be destroyed and
+  // invalidate its weak pointers before any other members are destroyed.
+  base::WeakPtrFactory<FileWriteHelper> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileWriteHelper);
+};
+
+}  // namespace gdata
+
+#endif  // CHROME_BROWSER_CHROMEOS_GDATA_FILE_WRITE_HELPER_H_