Improve error message for failing code insertion on about:-URLs

extensions/common/manifest_constants.h

 // Copyright 2013 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 EXTENSIONS_COMMON_MANIFEST_CONSTANTS_H_
 #define EXTENSIONS_COMMON_MANIFEST_CONSTANTS_H_
 
 namespace extensions {
 
 // Keys used in JSON representation of extensions.
@@ skipping 224 matching lines @@
 }  // namespace manifest_values
 
 // Error messages returned from extension installation.
 namespace manifest_errors {
 
 extern const char kActiveTabPermissionNotGranted[];
 extern const char kAllURLOrActiveTabNeeded[];
 extern const char kAppsNotEnabled[];
 extern const char kBackgroundPermissionNeeded[];
 extern const char kBackgroundRequiredForPlatformApps[];
+extern const char kCannotAccessAboutUrl[];
 extern const char kCannotAccessChromeUrl[];
 extern const char kCannotAccessExtensionUrl[];
 extern const char kCannotAccessPage[];
 extern const char kCannotChangeExtensionID[];
 extern const char kCannotClaimAllHostsInExtent[];
 extern const char kCannotClaimAllURLsInExtent[];
 extern const char kCannotScriptGallery[];
 extern const char kCannotScriptSigninPage[];
 extern const char kCannotUninstallManagedExtension[];
 extern const char kChromeVersionTooLow[];
@@ skipping 213 matching lines @@
 extern const char kWebRequestConflictsWithLazyBackground[];
 #if defined(OS_CHROMEOS)
 extern const char kIllegalPlugins[];
 #endif
 
 }  // namespace manifest_errors
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_MANIFEST_CONSTANTS_H_