Avoid return value from commitBeforeMutationEffects

This is an unusual flag that doesn't serve a special return value.

We can just use the global flag and reset it before the next mutation phase.
Unlike focusedInstanceHandle this doesn't leak any memory in the meantime.

Author: sebmarkbage

packages/react-reconciler/src/ReactFiberCommitWork.js

@@ -232,23 +232,20 @@ let inProgressLanes: Lanes | null = null;
 let inProgressRoot: FiberRoot | null = null;
 
 let focusedInstanceHandle: null | Fiber = null;
-let shouldFireAfterActiveInstanceBlur: boolean = false;
+export let shouldFireAfterActiveInstanceBlur: boolean = false;
 
 export function commitBeforeMutationEffects(
   root: FiberRoot,
   firstChild: Fiber,
-): boolean {
+): void {
   focusedInstanceHandle = prepareForCommit(root.containerInfo);
+  shouldFireAfterActiveInstanceBlur = false;
 
   nextEffect = firstChild;
   commitBeforeMutationEffects_begin();
 
   // We no longer need to track the active instance fiber
-  const shouldFire = shouldFireAfterActiveInstanceBlur;
-  shouldFireAfterActiveInstanceBlur = false;
   focusedInstanceHandle = null;
-
-  return shouldFire;
 }
 
 function commitBeforeMutationEffects_begin() {

packages/react-reconciler/src/ReactFiberWorkLoop.js

@@ -197,6 +197,7 @@ import {
 } from './ReactFiberThrow';
 import {
   commitBeforeMutationEffects,
+  shouldFireAfterActiveInstanceBlur,
   commitLayoutEffects,
   commitMutationEffects,
   commitPassiveMountEffects,
@@ -3361,10 +3362,7 @@ function commitRootImpl(
     // The first phase a "before mutation" phase. We use this phase to read the
     // state of the host tree right before we mutate it. This is where
     // getSnapshotBeforeUpdate is called.
-    const shouldFireAfterActiveInstanceBlur = commitBeforeMutationEffects(
-      root,
-      finishedWork,
-    );
+    commitBeforeMutationEffects(root, finishedWork);
 
     // The next phase is the mutation phase, where we mutate the host tree.
     commitMutationEffects(root, finishedWork, lanes);