Move String::truncate to StringImpl.

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 213 matching lines @@
     if (isNull())
         return;
     if (!is8Bit())
         return;
     if (unsigned length = this->length())
         m_impl = make16BitFrom8BitSource(m_impl->characters8(), length).releaseImpl();
     else
         m_impl = StringImpl::empty16Bit();
 }
 
-void String::truncate(unsigned position)
+void String::truncate(unsigned length)
 {
-    if (position >= length())
-        return;
-    if (m_impl->is8Bit()) {
-        LChar* data;
-        RefPtr<StringImpl> newImpl = StringImpl::createUninitialized(position, data);
-        memcpy(data, m_impl->characters8(), position * sizeof(LChar));
-        m_impl = newImpl.release();
-    } else {
-        UChar* data;
-        RefPtr<StringImpl> newImpl = StringImpl::createUninitialized(position, data);
-        memcpy(data, m_impl->characters16(), position * sizeof(UChar));
-        m_impl = newImpl.release();
-    }
+    if (m_impl)
+        m_impl = m_impl->truncate(length);
 }
 
 void String::remove(unsigned start, unsigned lengthToRemove)
 {
     if (m_impl)
         m_impl = m_impl->remove(start, lengthToRemove);
 }
 
 String String::substring(unsigned pos, unsigned len) const
 {
@@ skipping 629 matching lines @@
     buffer.append('\0');
     return buffer;
 }
 
 Vector<char> asciiDebug(String& string)
 {
     return asciiDebug(string.impl());
 }
 
 #endif