Fabric: Removing `Scheduler::rootComponentDescriptor_`

Summary:
This diff simplifies `ShadowTree` constructor by removing `rootComponentDescriptor` argument. It was previously stored and supplied by `Scheduler`; now `ShadowTree` class allocates one instance of it for all instances of `ShadowTree`. The `RootComponentDescriptor` instance of it is only needed to clone a `RootShadowNode` instance; it cannot issue events, state updates, or anything like that because it does not have React counterpart.

Changelog: [Internal] Fabric-specific internal change.

Reviewed By: JoshuaGross, sammy-SC

Differential Revision: D26048466

fbshipit-source-id: ec02b1b4bcc917efe17cef58112fa870b341c85f

ReactCommon/react/renderer/mounting/ShadowTree.cpp

@@ -222,22 +222,26 @@ ShadowTree::ShadowTree(
     SurfaceId surfaceId,
     LayoutConstraints const &layoutConstraints,
     LayoutContext const &layoutContext,
-    RootComponentDescriptor const &rootComponentDescriptor,
     ShadowTreeDelegate const &delegate,
     std::weak_ptr<MountingOverrideDelegate const> mountingOverrideDelegate)
     : surfaceId_(surfaceId), delegate_(delegate) {
   const auto noopEventEmitter = std::make_shared<const ViewEventEmitter>(
       nullptr, -1, std::shared_ptr<const EventDispatcher>());
 
+  static auto globalRootComponentDescriptor =
+      std::make_unique<RootComponentDescriptor const>(
+          ComponentDescriptorParameters{
+              EventDispatcher::Shared{}, nullptr, nullptr});
+
   const auto props = std::make_shared<const RootProps>(
       *RootShadowNode::defaultSharedProps(), layoutConstraints, layoutContext);
 
   auto const fragment =
       ShadowNodeFamilyFragment{surfaceId, surfaceId, noopEventEmitter};
-  auto family = rootComponentDescriptor.createFamily(fragment, nullptr);
+  auto family = globalRootComponentDescriptor->createFamily(fragment, nullptr);
 
   auto rootShadowNode = std::static_pointer_cast<const RootShadowNode>(
-      rootComponentDescriptor.createShadowNode(
+      globalRootComponentDescriptor->createShadowNode(
           ShadowNodeFragment{
               /* .props = */ props,
           },

ReactCommon/react/renderer/mounting/ShadowTree.h

@@ -67,7 +67,6 @@ class ShadowTree final {
       SurfaceId surfaceId,
       LayoutConstraints const &layoutConstraints,
       LayoutContext const &layoutContext,
-      RootComponentDescriptor const &rootComponentDescriptor,
       ShadowTreeDelegate const &delegate,
       std::weak_ptr<MountingOverrideDelegate const> mountingOverrideDelegate);
 

ReactCommon/react/renderer/mounting/tests/StateReconciliationTest.cpp

@@ -10,7 +10,6 @@
 #include <gtest/gtest.h>
 
 #include <react/renderer/componentregistry/ComponentDescriptorProviderRegistry.h>
-#include <react/renderer/components/root/RootComponentDescriptor.h>
 #include <react/renderer/components/view/ViewComponentDescriptor.h>
 #include <react/renderer/element/ComponentBuilder.h>
 #include <react/renderer/element/Element.h>
@@ -95,14 +94,10 @@ TEST(StateReconciliationTest, testStateReconciliation) {
   auto &family = shadowNodeAB->getFamily();
   auto state1 = shadowNodeAB->getState();
   auto shadowTreeDelegate = DummyShadowTreeDelegate{};
-  auto eventDispatcher = EventDispatcher::Shared{};
-  auto rootComponentDescriptor =
-      ComponentDescriptorParameters{eventDispatcher, nullptr, nullptr};
   ShadowTree shadowTree{
       SurfaceId{11},
       LayoutConstraints{},
       LayoutContext{},
-      rootComponentDescriptor,
       shadowTreeDelegate,
       {}};
 

ReactCommon/react/renderer/scheduler/Scheduler.cpp

@@ -76,9 +76,6 @@ Scheduler::Scheduler(
   componentDescriptorRegistry_ = schedulerToolbox.componentRegistryFactory(
       eventDispatcher, schedulerToolbox.contextContainer);
 
-  rootComponentDescriptor_ = std::make_unique<const RootComponentDescriptor>(
-      ComponentDescriptorParameters{eventDispatcher, nullptr, nullptr});
-
   uiManager->setBackgroundExecutor(schedulerToolbox.backgroundExecutor);
   uiManager->setDelegate(this);
   uiManager->setComponentDescriptorRegistry(componentDescriptorRegistry_);
@@ -188,7 +185,6 @@ void Scheduler::startSurface(
       surfaceId,
       layoutConstraints,
       layoutContext,
-      *rootComponentDescriptor_,
       *uiManager_,
       mountingOverrideDelegate);
 

ReactCommon/react/renderer/scheduler/Scheduler.h

@@ -123,7 +123,6 @@ class Scheduler final : public UIManagerDelegate {
  private:
   SchedulerDelegate *delegate_;
   SharedComponentDescriptorRegistry componentDescriptorRegistry_;
-  std::unique_ptr<const RootComponentDescriptor> rootComponentDescriptor_;
   RuntimeExecutor runtimeExecutor_;
   std::shared_ptr<UIManager> uiManager_;
   std::shared_ptr<const ReactNativeConfig> reactNativeConfig_;