Implement minlength for <input> and <textarea>.

Source/core/html/FormAssociatedElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * 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
@@ skipping 221 matching lines @@
 bool FormAssociatedElement::stepMismatch() const
 {
     return false;
 }
 
 bool FormAssociatedElement::tooLong() const
 {
     return false;
 }
 
+bool FormAssociatedElement::tooShort() const
+{
+    return false;
+}
+
 bool FormAssociatedElement::typeMismatch() const
 {
     return false;
 }
 
 bool FormAssociatedElement::valid() const
 {
     bool someError = typeMismatch() || stepMismatch() || rangeUnderflow() || rangeOverflow()
-        || tooLong() || patternMismatch() || valueMissing() || hasBadInput() || customError();
+        || tooLong() || tooShort() || patternMismatch() || valueMissing() || hasBadInput()
+        || customError();
     return !someError;
 }
 
 bool FormAssociatedElement::valueMissing() const
 {
     return false;
 }
 
 String FormAssociatedElement::customValidationMessage() const
 {
@@ skipping 85 matching lines @@
     visitor->trace(m_element);
     IdTargetObserver::trace(visitor);
 }
 
 void FormAttributeTargetObserver::idTargetChanged()
 {
     m_element->formAttributeTargetChanged();
 }
 
 } // namespace blink