Allow ChromeOS file selection dialog to be shown from shell windows.

chrome/browser/extensions/api/file_system/file_system_api.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.
 
 #include "chrome/browser/extensions/api/file_system/file_system_api.h"
 
 #include "base/bind.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "chrome/browser/extensions/shell_window_registry.h"
@@ skipping 86 matching lines @@
   if (!GetFilePathOfFileEntry(filesystem_name, filesystem_path,
                               render_view_host_, &file_path, &error_)) {
     return false;
   }
 
   result_.reset(base::Value::CreateStringValue(file_path.value()));
   return true;
 }
 
 // Handles showing a dialog to the user to ask for the filename for a file to
-// save.
+// save or open.
 class FileSystemPickerFunction::FilePicker : public SelectFileDialog::Listener {
  public:
   FilePicker(FileSystemPickerFunction* function,
              content::WebContents* web_contents,
              const FilePath& suggested_path,
              bool for_save)
       : suggested_path_(suggested_path),
         for_save_(for_save),
         function_(function) {
     select_file_dialog_ = SelectFileDialog::Create(this);
@@ skipping 157 matching lines @@
   file_system::ChooseFileOptions* options = params->options.get();
   if (options) {
     if (options->type.get() &&  *options->type == kSaveFileOption)
       for_save = true;
   }
 
   return ShowPicker(FilePath(), for_save);
 }
 
 }  // namespace extensions