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

chrome/browser/ui/android/validation_message_bubble_android.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 CHROME_BROWSER_UI_ANDROID_VALIDATION_MESSAGE_BUBBLE_ANDROID_H_
 #define CHROME_BROWSER_UI_ANDROID_VALIDATION_MESSAGE_BUBBLE_ANDROID_H_
 
 #include <jni.h>
 
 #include "base/android/scoped_java_ref.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "chrome/browser/ui/validation_message_bubble.h"
 
 namespace content {
 class RenderWidgetHost;
 }
 
 namespace gfx {
 class Rect;
 }
 
 // An implementation of ValidationMessageBubble for Android. This class is a
 // bridge to a Java implementation.
 class ValidationMessageBubbleAndroid : public chrome::ValidationMessageBubble {
  public:
   ValidationMessageBubbleAndroid(content::RenderWidgetHost* widget_host,
                                  const gfx::Rect& anchor_in_screen,
                                  const string16& main_text,
                                  const string16& sub_text);
   virtual ~ValidationMessageBubbleAndroid();
   virtual void MoveOnAnchor(content::RenderWidgetHost* widget_host,
                             const gfx::Rect& anchor_in_screen);
 
   static bool Register(JNIEnv* env);
 
  private:
   base::android::ScopedJavaGlobalRef<jobject> java_validation_message_bubble_;
 };
 
 #endif  // CHROME_BROWSER_UI_ANDROID_VALIDATION_MESSAGE_BUBBLE_ANDROID_H_