Use a direct include of strings headers in chrome/browser/a*-c*/.

chrome/browser/android/intent_helper.h

 // 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.
 
 #ifndef CHROME_BROWSER_ANDROID_INTENT_HELPER_H_
 #define CHROME_BROWSER_ANDROID_INTENT_HELPER_H_
 
 #include <jni.h>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 
 namespace chrome {
 namespace android {
 
 // Triggers a send email intent.
 void SendEmail(const string16& data_email,
                const string16& data_subject,
                const string16& data_body,
                const string16& data_chooser_title,
                const string16& data_file_to_attach);
 
 bool RegisterIntentHelper(JNIEnv* env);
 
 }  // namespace android
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_ANDROID_INTENT_HELPER_H_