Remove unused variable. No bug, r+sr+a-ish=roc on irc.

content/base/src/nsContentUtils.cpp

@@ -3544,7 +3544,6 @@ nsresult
 nsContentUtils::HoldJSObjects(void* aScriptObjectHolder,
                               nsScriptObjectTracer* aTracer)
 {
-  PRBool newHolder;
   nsresult rv = sXPConnect->AddJSHolder(aScriptObjectHolder, aTracer);
   NS_ENSURE_SUCCESS(rv, rv);