Introduce apps API target in //apps and move app.runtime API into it

apps/browser/file_handler_util.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 APPS_BROWSER_FILE_HANDLER_UTIL_H_
+#define APPS_BROWSER_FILE_HANDLER_UTIL_H_
+
+#include <string>
+
+namespace apps {
+namespace file_handler_util {
+
+// Refers to a file entry that a renderer has been given access to.
+struct GrantedFileEntry {
+  GrantedFileEntry();
+  ~GrantedFileEntry();
+
+  std::string id;
+  std::string filesystem_id;
+  std::string registered_name;
+};
+
+}  // namespace file_handler_util
+}  // namespace apps
+
+#endif  // APPS_BROWSER_FILE_HANDLER_UTIL_H_