Use a direct include of strings headers in ui/, part 3.

ui/gfx/insets.cc

 // Copyright (c) 2009 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 "ui/gfx/insets.h"
 
 #if defined(TOOLKIT_GTK)
 #include <gtk/gtk.h>
 #endif
 
-#include "base/stringprintf.h"
+#include "base/strings/stringprintf.h"
 
 namespace gfx {
 
 template class InsetsBase<Insets, int>;
 
 Insets::Insets() : InsetsBase<Insets, int>(0, 0, 0, 0) {}
 
 Insets::Insets(int top, int left, int bottom, int right)
     : InsetsBase<Insets, int>(top, left, bottom, right) {}
 
 #if defined(TOOLKIT_GTK)
 Insets::Insets(const GtkBorder& border)
     : InsetsBase<Insets, int>(border.top,
                               border.left,
                               border.bottom,
                               border.right) {
 }
 #endif
 
 Insets::~Insets() {}
 
 std::string Insets::ToString() const {
   // Print members in the same order of the constructor parameters.
   return base::StringPrintf("%d,%d,%d,%d", top(),  left(), bottom(), right());
 }
 
 }  // namespace gfx