Update the remaining include paths of base/string_piece.h to its new location.

ui/base/resource/resource_handle.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 UI_BASE_RESOURCE_RESOURCE_HANDLE_H_
 #define UI_BASE_RESOURCE_RESOURCE_HANDLE_H_
 
 #include "base/basictypes.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 #include "ui/base/layout.h"
 #include "ui/base/ui_export.h"
 
 namespace base {
 class RefCountedStaticMemory;
 }
 
 namespace ui {
 
 class UI_EXPORT ResourceHandle {
@@ skipping 25 matching lines @@
   virtual TextEncodingType GetTextEncodingType() const = 0;
 
   // The scale of images in this resource pack relative to images in the 1x
   // resource pak.
   virtual ScaleFactor GetScaleFactor() const = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_RESOURCE_RESOURCE_HANDLE_H_