Ensure effects are reused when bailing out on the child

scripts/fiber/tests-failing.txt

@@ -46,9 +46,6 @@ src/renderers/shared/__tests__/ReactPerf-test.js
 * should not count time in a portal towards lifecycle method
 * should work when measurement starts during reconciliation
 
-src/renderers/shared/fiber/__tests__/ReactIncrementalSideEffects-test.js
-* can defer side-effects and reuse them later - complex
-
 src/renderers/shared/hooks/__tests__/ReactComponentTreeHook-test.js
 * can be retrieved by ID
 

scripts/fiber/tests-passing.txt

@@ -1231,6 +1231,7 @@ src/renderers/shared/fiber/__tests__/ReactIncrementalSideEffects-test.js
 * can update a completed tree before it has a chance to commit
 * updates a child even though the old props is empty
 * can defer side-effects and resume them later on
+* can defer side-effects and reuse them later - complex
 * deprioritizes setStates that happens within a deprioritized tree
 * calls callback after update is flushed
 * calls setState callback even if component bails out

src/renderers/shared/fiber/ReactFiberScheduler.js

@@ -494,6 +494,23 @@ module.exports = function<T, P, I, TI, C, CX, CI>(config : HostConfig<T, P, I, T
     }
   }
 
+  function reuseChildrenEffects(returnFiber : Fiber, firstChild : Fiber) {
+    let child = firstChild;
+    do {
+      // Ensure that the first and last effect of the parent corresponds
+      // to the children's first and last effect.
+      if (!returnFiber.firstEffect) {
+        returnFiber.firstEffect = child.firstEffect;
+      }
+      if (child.lastEffect) {
+        if (returnFiber.lastEffect) {
+          returnFiber.lastEffect.nextEffect = child.firstEffect;
+        }
+        returnFiber.lastEffect = child.lastEffect;
+      }
+    } while (child = child.sibling);
+  }
+
   function performUnitOfWork(workInProgress : Fiber) : ?Fiber {
 
     // The current, flushed, state of this fiber is the alternate.
@@ -513,6 +530,14 @@ module.exports = function<T, P, I, TI, C, CX, CI>(config : HostConfig<T, P, I, T
     }
 
     if (!next) {
+      const child = workInProgress.child;
+
+      if (child) {
+        // If we bailed out, ensure that we don't drop the effects from
+        // the subtree.
+        reuseChildrenEffects(workInProgress, child);
+      }
+
       if (__DEV__ && ReactFiberInstrumentation.debugTool) {
         ReactFiberInstrumentation.debugTool.onWillCompleteWork(workInProgress);
       }

src/renderers/shared/fiber/__tests__/ReactIncrementalSideEffects-test.js

@@ -831,9 +831,9 @@ describe('ReactIncrementalSideEffects', () => {
         // Updated.
         span(1),
         div(
+          span(1),
           // Still not updated.
           span(0),
-          span(0),
           span(0)
         )
       ),