Avoid sync IPCs for FileSystem API

chrome/renderer/permission_request_map.h

+// Copyright 2014 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 CONTENT_CHILD_FILEAPI_PERMISSION_REQUEST_MAP_H_
+#define CONTENT_CHILD_FILEAPI_PERMISSION_REQUEST_MAP_H_
+
+#include "base/id_map.h"
+
+namespace blink {
+class WebPermissionCallbacks;
+}
+
+namespace content {
+
+class PermissionRequestMap {
+ public:
+  static PermissionRequestMap* Get();
+
+  static PermissionRequestMap* GetOrCreate();
+
+  virtual ~PermissionRequestMap();
+
+  int RegisterPermissionCallbacks(
+      const blink::WebPermissionCallbacks& permission_callbacks);
+
+  blink::WebPermissionCallbacks* GetAndUnregisterCallbacks(int callbacks_id);
+
+ private:
+  PermissionRequestMap();
+
+  IDMap<blink::WebPermissionCallbacks> permission_request_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(PermissionRequestMap);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_CHILD_FILEAPI_PERMISSION_REQUEST_MAP_H_