Implement minlength for <input> and <textarea>.

Source/core/html/HTMLTextAreaElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2010 Apple Inc. All rights reserved.
  *
  * 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 29 matching lines @@
     int rows() const { return m_rows; }
 
     bool shouldWrapText() const { return m_wrap != NoWrap; }
 
     virtual String value() const OVERRIDE;
     void setValue(const String&, TextFieldEventBehavior = DispatchNoEvent);
     String defaultValue() const;
     void setDefaultValue(const String&);
     int textLength() const { return value().length(); }
     int maxLength() const;
+    int minLength() const;
     void setMaxLength(int, ExceptionState&);
+    void setMinLength(int, ExceptionState&);
 
     String suggestedValue() const;
     void setSuggestedValue(const String&);
 
     // For ValidityState
     virtual String validationMessage() const OVERRIDE;
     virtual bool valueMissing() const OVERRIDE;
     virtual bool tooLong() const OVERRIDE;
+    virtual bool tooShort() const OVERRIDE;
     bool isValidValue(const String&) const;
 
     void setCols(int);
     void setRows(int);
 
 private:
     HTMLTextAreaElement(Document&, HTMLFormElement*);
 
     enum WrapMethod { NoWrap, SoftWrap, HardWrap };
 
@@ skipping 46 matching lines @@
     virtual bool isKeyboardFocusable() const OVERRIDE;
     virtual void updateFocusAppearance(bool restorePreviousSelection) OVERRIDE;
 
     virtual void accessKeyAction(bool sendMouseEvents) OVERRIDE;
 
     virtual bool matchesReadOnlyPseudoClass() const OVERRIDE;
     virtual bool matchesReadWritePseudoClass() const OVERRIDE;
 
     bool valueMissing(const String& value) const { return isRequiredFormControl() && !isDisabledOrReadOnly() && value.isEmpty(); }
     bool tooLong(const String&, NeedsToCheckDirtyFlag) const;
+    bool tooShort(const String&, NeedsToCheckDirtyFlag) const;
 
     int m_rows;
     int m_cols;
     WrapMethod m_wrap;
     mutable String m_value;
     mutable bool m_isDirty;
     bool m_valueIsUpToDate;
     String m_suggestedValue;
 };
 
 } //namespace
 
 #endif