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

chrome/common/extensions/api/webstore_api_constants.cc

Index: chrome/common/extensions/api/webstore_api_constants.cc
diff --git a/chrome/common/extensions/api/webstore_api_constants.cc b/chrome/common/extensions/api/webstore_api_constants.cc
new file mode 100644
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+++ b/chrome/common/extensions/api/webstore_api_constants.cc
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+// 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.
+
+#include "chrome/common/extensions/api/webstore_api_constants.h"
+
+namespace extensions {
+namespace api {
+namespace webstore {
+
+// The "downloading" stage begins when the installer starts downloading modules
+// for the extension.
+const char kInstallStageDownloading[] = "downloading";
+
+// The "installing" stage begins once all downloads are complete, and the
+// CrxInstaller begins.
+const char kInstallStageInstalling[] = "installing";
+
+// The method in custom_webstore_bindings.js triggered when we enter a new
+// install stage ("downloading" or "installing").
+const char kOnInstallStageChangedMethodName[] = "onInstallStageChanged";
+
+// The method in custom_webstore_bindings.js triggered when we update
+// download progress.
+const char kOnDownloadProgressMethodName[] = "onDownloadProgress";
+
+}  // namespace webstore
+}  // namespace api
+}  // namespace extensions