Improve <textarea> validation performance.

Source/core/html/HTMLTextAreaElement.h

Index: Source/core/html/HTMLTextAreaElement.h
diff --git a/Source/core/html/HTMLTextAreaElement.h b/Source/core/html/HTMLTextAreaElement.h
index 5552c8e0b520a0f1dcd5b2e7cb1c098275c5bdfe..1b47ac7c24ee870bac25578399f946056a8a9eb7 100644
--- a/Source/core/html/HTMLTextAreaElement.h
+++ b/Source/core/html/HTMLTextAreaElement.h
@@ -121,8 +121,9 @@ private:
     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;
+    // If the String* argument is 0, apply this->value().
+    bool valueMissing(const String*) const;
+    bool tooLong(const String*, NeedsToCheckDirtyFlag) const;
 
     int m_rows;
     int m_cols;