Include <algorithm> if you use functions from <algorithm>.

third_party/WebKit/Source/wtf/text/WTFString.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007-2009 Torch Mobile, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 16 matching lines @@
 #include "wtf/DataLog.h"
 #include "wtf/HexNumber.h"
 #include "wtf/MathExtras.h"
 #include "wtf/StringExtras.h"
 #include "wtf/Vector.h"
 #include "wtf/dtoa.h"
 #include "wtf/text/CString.h"
 #include "wtf/text/CharacterNames.h"
 #include "wtf/text/UTF8.h"
 #include "wtf/text/Unicode.h"
+#include <algorithm>
 #include <stdarg.h>
 
 namespace WTF {
 
 using namespace Unicode;
 
 // Construct a string with UTF-16 data.
 String::String(const UChar* characters, unsigned length)
     : m_impl(characters ? StringImpl::create(characters, length) : nullptr)
 {
@@ skipping 1174 matching lines @@
     buffer.append('\0');
     return buffer;
 }
 
 Vector<char> asciiDebug(String& string)
 {
     return asciiDebug(string.impl());
 }
 
 #endif