run iwyu on base!

base/string_piece.cc

 // Copyright (c) 2006-2008 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.
 // Copied from strings/stringpiece.cc with modifications
 
+#include <limits.h>
+#include <stddef.h>
+#include <string.h>
 #include <algorithm>
 #include <ostream>
+#include <string>
 
 #include "base/string_piece.h"
 
 namespace base {
 
 typedef StringPiece::size_type size_type;
 
 std::ostream& operator<<(std::ostream& o, const StringPiece& piece) {
   o.write(piece.data(), static_cast<std::streamsize>(piece.size()));
   return o;
@@ skipping 192 matching lines @@
 
 StringPiece StringPiece::substr(size_type pos, size_type n) const {
   if (pos > length_) pos = length_;
   if (n > length_ - pos) n = length_ - pos;
   return StringPiece(ptr_ + pos, n);
 }
 
 const StringPiece::size_type StringPiece::npos = size_type(-1);
 
 }  // namespace base