Backed out changeset 181a123cd227 (bug 1629022) by jonco's request CLOSED TREE

xpcom/base/CycleCollectedJSRuntime.cpp

@@ -1181,25 +1181,26 @@ static inline void CheckHolderIsSingleZone(
   aParticipant->Trace(aHolder, tracer, nullptr);
 }
 
-#endif
-
 static inline bool ShouldCheckSingleZoneHolders() {
-#if defined(DEBUG)
+#  ifdef DEBUG
   return true;
-#elif defined(NIGHTLY_BUILD) || defined(MOZ_DEV_EDITION)
+#  else
   // Don't check every time to avoid performance impact.
   return rand() % 256 == 0;
-#else
-  return false;
 #  endif
 }
 
+#endif
+
 void CycleCollectedJSRuntime::TraceNativeGrayRoots(JSTracer* aTracer) {
   // NB: This is here just to preserve the existing XPConnect order. I doubt it
   // would hurt to do this after the JS holders.
   TraceAdditionalNativeGrayRoots(aTracer);
 
+#ifdef CHECK_SINGLE_ZONE_JS_HOLDERS
   bool checkSingleZoneHolders = ShouldCheckSingleZoneHolders();
+#endif
+
   mJSHolders.ForEach([aTracer, checkSingleZoneHolders](
                          void* holder, nsScriptObjectTracer* tracer) {
 #ifdef CHECK_SINGLE_ZONE_JS_HOLDERS