Backout Bug 747675 to see if it has caused startup crashes

content/base/src/nsCCUncollectableMarker.cpp

@@ -362,6 +362,12 @@ nsCCUncollectableMarker::Observe(nsISupports* aSubject, const char* aTopic,
     }
   }
 
+  if (cleanupJS) {
+    nsContentUtils::UnmarkGrayJSListenersInCCGenerationDocuments(sGeneration);
+    MarkMessageManagers();
+    xpc_UnmarkSkippableJSHolders();
+  }
+
 #ifdef MOZ_XUL
   nsXULPrototypeCache* xulCache = nsXULPrototypeCache::GetInstance();
   if (xulCache) {
@@ -369,18 +375,6 @@ nsCCUncollectableMarker::Observe(nsISupports* aSubject, const char* aTopic,
   }
 #endif
 
-  static bool previousWasJSCleanup = false;
-  if (cleanupJS) {
-    nsContentUtils::UnmarkGrayJSListenersInCCGenerationDocuments(sGeneration);
-    MarkMessageManagers();
-    previousWasJSCleanup = true;
-  } else if (previousWasJSCleanup) {
-    previousWasJSCleanup = false;
-    if (!prepareForCC) {
-      xpc_UnmarkSkippableJSHolders();
-    }
-  }
-
   return NS_OK;
 }