Move about://-related constants from //content to //url

url/url_constants.cc

 // 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 "url/url_constants.h"
 
 namespace url {
 
+const char kAboutBlankURL[] = "about:blank";
+
+const char kAboutScheme[] = "about";
 const char kBlobScheme[] = "blob";
 const char kDataScheme[] = "data";
 const char kFileScheme[] = "file";
 const char kFileSystemScheme[] = "filesystem";
 const char kFtpScheme[] = "ftp";
 const char kHttpScheme[] = "http";
 const char kHttpsScheme[] = "https";
 const char kJavaScriptScheme[] = "javascript";
 const char kMailToScheme[] = "mailto";
 const char kWsScheme[] = "ws";
 const char kWssScheme[] = "wss";
 
 const char kStandardSchemeSeparator[] = "://";
 
 }  // namespace url