[Extensions] Rework inline installation observation

chrome/common/extensions/webstore_install_result.cc

+// Copyright 2016 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/webstore_install_result.h"
+
+namespace extensions {
+namespace webstore_install {
+
+const char kInvalidWebstoreItemId[] = "Invalid Chrome Web Store item ID";
+const char kWebstoreRequestError[] =
+    "Could not fetch data from the Chrome Web Store";
+const char kInvalidWebstoreResponseError[] = "Invalid Chrome Web Store reponse";
+const char kInvalidManifestError[] = "Invalid manifest";
+const char kUserCancelledError[] = "User cancelled install";
+const char kExtensionIsBlacklisted[] = "Extension is blacklisted";
+const char kInstallInProgressError[] = "An install is already in progress";
+
+}  // namespace webstore_install
+}  // namespace extensions