fix[devtools/updateFiberRecursively]: mount suspense fallback set in timed-out case

Author: hoxyq

packages/react-devtools-shared/src/backend/renderer.js

@@ -2345,6 +2345,18 @@ export function attach(
       const prevFallbackChildSet = prevFiberChild
         ? prevFiberChild.sibling
         : null;
+
+      if (prevFallbackChildSet == null && nextFallbackChildSet != null) {
+        mountFiberRecursively(
+          nextFallbackChildSet,
+          shouldIncludeInTree ? nextFiber : parentFiber,
+          true,
+          traceNearestHostComponentUpdate,
+        );
+
+        shouldResetChildren = true;
+      }
+
       if (
         nextFallbackChildSet != null &&
         prevFallbackChildSet != null &&

packages/react-devtools-shared/src/hook.js

@@ -320,7 +320,7 @@ export function installHook(target: any): DevToolsHook | null {
 
   let uidCounter = 0;
 
-  function inject(renderer: ReactRenderer) {
+  function inject(renderer: ReactRenderer): number {
     const id = ++uidCounter;
     renderers.set(id, renderer);