Improve <textarea> validation performance.

Source/core/html/HTMLTextAreaElement.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, 2008, 2010 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2007 Samuel Weinig (sam@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 472 matching lines @@
         return locale().queryString(blink::WebLocalizedString::ValidationValueMissing);
 
     if (tooLong())
         return locale().validationMessageTooLongText(computeLengthForSubmission(value()), maxLength());
 
     return String();
 }
 
 bool HTMLTextAreaElement::valueMissing() const
 {
-    return willValidate() && valueMissing(value());
+    // We should not call value() for performance.
+    return willValidate() && valueMissing(0);
+}
+
+bool HTMLTextAreaElement::valueMissing(const String* value) const
+{
+    return isRequiredFormControl() && !isDisabledOrReadOnly() && (value ? *value : this->value()).isEmpty();
 }
 
 bool HTMLTextAreaElement::tooLong() const
 {
-    return willValidate() && tooLong(value(), CheckDirtyFlag);
+    // We should not call value() for performance.
+    return willValidate() && tooLong(0, CheckDirtyFlag);
 }
 
-bool HTMLTextAreaElement::tooLong(const String& value, NeedsToCheckDirtyFlag check) const
+bool HTMLTextAreaElement::tooLong(const String* value, NeedsToCheckDirtyFlag check) const
 {
     // Return false for the default value or value set by script even if it is
     // longer than maxLength.
     if (check == CheckDirtyFlag && !lastChangeWasUserEdit())
         return false;
 
     int max = maxLength();
     if (max < 0)
         return false;
-    return computeLengthForSubmission(value) > static_cast<unsigned>(max);
+    return computeLengthForSubmission(value ? *value : this->value()) > static_cast<unsigned>(max);
 }
 
 bool HTMLTextAreaElement::isValidValue(const String& candidate) const
 {
-    return !valueMissing(candidate) && !tooLong(candidate, IgnoreDirtyFlag);
+    return !valueMissing(&candidate) && !tooLong(&candidate, IgnoreDirtyFlag);
 }
 
 void HTMLTextAreaElement::accessKeyAction(bool)
 {
     focus();
 }
 
 void HTMLTextAreaElement::setCols(int cols)
 {
     setIntegralAttribute(colsAttr, cols);
@@ skipping 37 matching lines @@
 {
     return true;
 }
 
 bool HTMLTextAreaElement::supportsAutofocus() const
 {
     return true;
 }
 
 }