Use a direct include of strings headers in url/, win8/.

url/gurl.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 URL_GURL_H_
 #define URL_GURL_H_
 
 #include <iosfwd>
 #include <string>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "url/url_canon.h"
 #include "url/url_canon_stdstring.h"
 #include "url/url_export.h"
 #include "url/url_parse.h"
 
 class URL_EXPORT GURL {
  public:
   typedef url_canon::StdStringReplacements<std::string> Replacements;
   typedef url_canon::StdStringReplacements<string16> ReplacementsW;
 
@@ skipping 334 matching lines @@
   // Used for nested schemes [currently only filesystem:].
   GURL* inner_url_;
 
   // TODO bug 684583: Add encoding for query params.
 };
 
 // Stream operator so GURL can be used in assertion statements.
 URL_EXPORT std::ostream& operator<<(std::ostream& out, const GURL& url);
 
 #endif  // URL_GURL_H_