Bug 767806 - Don't create a useless string every time we check for input's validity. r=jlebar

content/html/content/src/nsHTMLInputElement.cpp

@@ -3674,12 +3674,14 @@ nsHTMLInputElement::HasTypeMismatch() const
 bool
 nsHTMLInputElement::HasPatternMismatch() const
 {
-  nsAutoString pattern;
   if (!DoesPatternApply() ||
-      !GetAttr(kNameSpaceID_None, nsGkAtoms::pattern, pattern)) {
+      !HasAttr(kNameSpaceID_None, nsGkAtoms::pattern)) {
     return false;
   }
 
+  nsAutoString pattern;
+  GetAttr(kNameSpaceID_None, nsGkAtoms::pattern, pattern);
+
   nsAutoString value;
   NS_ENSURE_SUCCESS(GetValueInternal(value), false);