Add chrome.webstore API methods to allow sites to see progress of installation

chrome/common/extensions/api/webstore/webstore_api_constants.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 CHROME_COMMON_EXTENSIONS_API_WEBSTORE_WEBSTORE_API_CONSTANTS_H_
+#define CHROME_COMMON_EXTENSIONS_API_WEBSTORE_WEBSTORE_API_CONSTANTS_H_
+
+namespace extensions {
+namespace api {
+namespace webstore {
+
+// An enum for listener types. This is used when creating/reading the mask for
+// IPC messages.
+enum ListenerType {
+  INSTALL_STAGE_LISTENER = 1,
+  DOWNLOAD_PROGRESS_LISTENER
+};
+
+extern const char kInstallStageDownloading[];
+extern const char kInstallStageInstalling[];
+extern const char kOnInstallStageChangedMethodName[];
+extern const char kOnDownloadProgressMethodName[];
+
+}  // namespace webstore
+}  // namespace api
+}  // namespace extensions
+
+#endif  // CHROME_COMMON_EXTENSIONS_API_WEBSTORE_WEBSTORE_API_CONSTANTS_H_