Bug 537572 - 'Workers: nsLayoutStatics refcounting isn't threadsafe, triggered via nsContentUtils::WrapNative'. r=bent.

layout/build/nsLayoutStatics.cpp

@@ -395,6 +395,9 @@ nsLayoutStatics::Shutdown()
 void
 nsLayoutStatics::AddRef()
 {
+  NS_ASSERTION(NS_IsMainThread(),
+               "nsLayoutStatics reference counting must be on main thread");
+
   NS_ASSERTION(sLayoutStaticRefcnt,
                "nsLayoutStatics already dropped to zero!");
 
@@ -406,6 +409,9 @@ nsLayoutStatics::AddRef()
 void
 nsLayoutStatics::Release()
 {
+  NS_ASSERTION(NS_IsMainThread(),
+               "nsLayoutStatics reference counting must be on main thread");
+
   --sLayoutStaticRefcnt;
   NS_LOG_RELEASE(&sLayoutStaticRefcnt, sLayoutStaticRefcnt,
                  "nsLayoutStatics");