Fiber DOM async feature flag (#9127)

D4662171

src/renderers/dom/fiber/ReactDOMFiber.js

@@ -330,7 +330,7 @@ var DOMRenderer = ReactFiberReconciler({
 
   scheduleDeferredCallback: ReactDOMFrameScheduling.rIC,
 
-  useSyncScheduling: true,
+  useSyncScheduling: !ReactDOMFeatureFlags.fiberAsyncScheduling,
 
 });
 

src/renderers/dom/shared/ReactDOMFeatureFlags.js

@@ -12,6 +12,7 @@
 'use strict';
 
 var ReactDOMFeatureFlags = {
+  fiberAsyncScheduling: false,
   useCreateElement: true,
   useFiber: false,
 };

src/renderers/shared/shared/event/EventPluginHub.js

@@ -126,9 +126,12 @@ var EventPluginHub = {
     // TODO: shouldPreventMouseEvent is DOM-specific and definitely should not
     // live here; needs to be moved to a better place soon
     if (typeof inst.tag === 'number') {
-      const props = EventPluginUtils.getFiberCurrentPropsFromNode(
-        inst.stateNode
-      );
+      const stateNode = inst.stateNode;
+      if (!stateNode) {
+        // Work in progress (ex: onload events in incremental mode).
+        return null;
+      }
+      const props = EventPluginUtils.getFiberCurrentPropsFromNode(stateNode);
       if (!props) {
         // Work in progress.
         return null;