Back out "Delete RuntimeScheduler yielding mobile config"

Summary:
D33740360 (https://github.com/facebook/react-native/commit/16ed62a850dd81bd9cc7f77ab3e77f42ed64b177) broke Explore VR on React Native. The app would go into a loop on boot and not finish mounting. This is probably a product code issue, but it's not a trivial issue to solve. Unlanding to unblock the RN migration.

Changelog:

[internal] internal

Reviewed By: mdvacca

Differential Revision: D33918026

fbshipit-source-id: cc77c70ece9994d82c91f7ae8783e959629e9cfb

React/Fabric/RCTSurfacePresenter.mm

@@ -271,6 +271,8 @@ static BackgroundExecutor RCTGetBackgroundExecutor()
   auto weakRuntimeScheduler = _contextContainer->find<std::weak_ptr<RuntimeScheduler>>("RuntimeScheduler");
   auto runtimeScheduler = weakRuntimeScheduler.hasValue() ? weakRuntimeScheduler.value().lock() : nullptr;
   if (runtimeScheduler) {
+    runtimeScheduler->setEnableYielding(
+        reactNativeConfig->getBool("react_native_new_architecture:runtimescheduler_enable_yielding_ios"));
     runtimeExecutor = [runtimeScheduler](std::function<void(jsi::Runtime & runtime)> &&callback) {
       runtimeScheduler->scheduleWork(std::move(callback));
     };

ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.cpp

@@ -369,6 +369,8 @@ void Binding::installFabricUIManager(
   if (runtimeSchedulerHolder) {
     auto runtimeScheduler = runtimeSchedulerHolder->cthis()->get().lock();
     if (runtimeScheduler) {
+      runtimeScheduler->setEnableYielding(config->getBool(
+          "react_native_new_architecture:runtimescheduler_enable_yielding_android"));
       runtimeExecutor =
           [runtimeScheduler](
               std::function<void(jsi::Runtime & runtime)> &&callback) {

ReactCommon/react/renderer/runtimescheduler/RuntimeScheduler.cpp

@@ -22,13 +22,19 @@ RuntimeScheduler::RuntimeScheduler(
 
 void RuntimeScheduler::scheduleWork(
     std::function<void(jsi::Runtime &)> callback) const {
-  shouldYield_ = true;
-  runtimeExecutor_(
-      [this, callback = std::move(callback)](jsi::Runtime &runtime) {
-        shouldYield_ = false;
-        callback(runtime);
-        startWorkLoop(runtime);
-      });
+  if (enableYielding_) {
+    shouldYield_ = true;
+    runtimeExecutor_(
+        [this, callback = std::move(callback)](jsi::Runtime &runtime) {
+          shouldYield_ = false;
+          callback(runtime);
+          startWorkLoop(runtime);
+        });
+  } else {
+    runtimeExecutor_([callback = std::move(callback)](jsi::Runtime &runtime) {
+      callback(runtime);
+    });
+  }
 }
 
 std::shared_ptr<Task> RuntimeScheduler::scheduleTask(
@@ -64,6 +70,10 @@ RuntimeSchedulerTimePoint RuntimeScheduler::now() const noexcept {
   return now_();
 }
 
+void RuntimeScheduler::setEnableYielding(bool enableYielding) {
+  enableYielding_ = enableYielding;
+}
+
 void RuntimeScheduler::executeNowOnTheSameThread(
     std::function<void(jsi::Runtime &runtime)> callback) {
   shouldYield_ = true;

ReactCommon/react/renderer/runtimescheduler/RuntimeScheduler.h

@@ -106,6 +106,7 @@ class RuntimeScheduler final {
    * Thread synchronization must be enforced externally.
    */
   void callImmediates(jsi::Runtime &runtime);
+  void setEnableYielding(bool enableYielding);
 
  private:
   mutable std::priority_queue<
@@ -139,6 +140,15 @@ class RuntimeScheduler final {
    */
   mutable std::atomic_bool isWorkLoopScheduled_{false};
 
+  /*
+   * Flag indicating if yielding is enabled.
+   *
+   * If set to true and Concurrent Mode is enabled on the surface,
+   * React Native will ask React to yield in case any work has been scheduled.
+   * Default value is false
+   */
+  bool enableYielding_{false};
+
   /*
    * This flag is set while performing work, to prevent re-entrancy.
    */

ReactCommon/react/renderer/runtimescheduler/tests/RuntimeSchedulerTest.cpp

@@ -323,7 +323,7 @@ TEST_F(RuntimeSchedulerTest, scheduleWork) {
 
   EXPECT_FALSE(wasCalled);
 
-  EXPECT_TRUE(runtimeScheduler_->getShouldYield());
+  EXPECT_FALSE(runtimeScheduler_->getShouldYield());
 
   EXPECT_EQ(stubQueue_->size(), 1);
 
@@ -334,6 +334,7 @@ TEST_F(RuntimeSchedulerTest, scheduleWork) {
 }
 
 TEST_F(RuntimeSchedulerTest, scheduleWorkWithYielding) {
+  runtimeScheduler_->setEnableYielding(true);
   bool wasCalled = false;
   runtimeScheduler_->scheduleWork(
       [&](jsi::Runtime const &) { wasCalled = true; });
@@ -352,6 +353,8 @@ TEST_F(RuntimeSchedulerTest, scheduleWorkWithYielding) {
 }
 
 TEST_F(RuntimeSchedulerTest, normalTaskYieldsToPlatformEvent) {
+  runtimeScheduler_->setEnableYielding(true);
+
   bool didRunJavaScriptTask = false;
   bool didRunPlatformWork = false;
 
@@ -379,6 +382,8 @@ TEST_F(RuntimeSchedulerTest, normalTaskYieldsToPlatformEvent) {
 }
 
 TEST_F(RuntimeSchedulerTest, expiredTaskDoesntYieldToPlatformEvent) {
+  runtimeScheduler_->setEnableYielding(true);
+
   bool didRunJavaScriptTask = false;
   bool didRunPlatformWork = false;
 
@@ -407,6 +412,8 @@ TEST_F(RuntimeSchedulerTest, expiredTaskDoesntYieldToPlatformEvent) {
 }
 
 TEST_F(RuntimeSchedulerTest, immediateTaskDoesntYieldToPlatformEvent) {
+  runtimeScheduler_->setEnableYielding(true);
+
   bool didRunJavaScriptTask = false;
   bool didRunPlatformWork = false;