Use a direct include of strings headers in base/.

base/guid_posix.cc

 // Copyright (c) 2012 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 "base/guid.h"
 
 #include "base/rand_util.h"
-#include "base/stringprintf.h"
+#include "base/strings/stringprintf.h"
 
 namespace base {
 
 std::string GenerateGUID() {
   uint64 sixteen_bytes[2] = { base::RandUint64(), base::RandUint64() };
   return RandomDataToGUIDString(sixteen_bytes);
 }
 
 // TODO(cmasone): Once we're comfortable this works, migrate Windows code to
 // use this as well.
 std::string RandomDataToGUIDString(const uint64 bytes[2]) {
   return StringPrintf("%08X-%04X-%04X-%04X-%012llX",
                       static_cast<unsigned int>(bytes[0] >> 32),
                       static_cast<unsigned int>((bytes[0] >> 16) & 0x0000ffff),
                       static_cast<unsigned int>(bytes[0] & 0x0000ffff),
                       static_cast<unsigned int>(bytes[1] >> 48),
                       bytes[1] & 0x0000ffffffffffffULL);
 }
 
 }  // namespace guid