Expose scheduler through RCTSurfacePresenter

Summary:
Exposes event listener through iOS scheduler wrapper (`RCTScheduler`) and exposes scheduler itself through `RCTSurfacePresenter`.

Changelog: [Changed] Exposed `RCTScheduler` to allow setting event listeners.

Reviewed By: philIip

Differential Revision: D35313398

fbshipit-source-id: 794179d47f407fee5692a98b13ac08f92e85a61c

React/Fabric/RCTScheduler.h

@@ -10,6 +10,7 @@
 
 #import <react/renderer/componentregistry/ComponentDescriptorFactory.h>
 #import <react/renderer/core/ComponentDescriptor.h>
+#import <react/renderer/core/EventListener.h>
 #import <react/renderer/core/LayoutConstraints.h>
 #import <react/renderer/core/LayoutContext.h>
 #import <react/renderer/mounting/MountingCoordinator.h>
@@ -64,6 +65,10 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)animationTick;
 
+- (void)addEventListener:(std::shared_ptr<facebook::react::EventListener> const &)listener;
+
+- (void)removeEventListener:(std::shared_ptr<facebook::react::EventListener> const &)listener;
+
 @end
 
 NS_ASSUME_NONNULL_END

React/Fabric/RCTScheduler.mm

@@ -193,4 +193,14 @@ - (void)onAllAnimationsComplete
   }
 }
 
+- (void)addEventListener:(std::shared_ptr<EventListener> const &)listener
+{
+  return _scheduler->addEventListener(listener);
+}
+
+- (void)removeEventListener:(std::shared_ptr<EventListener> const &)listener
+{
+  return _scheduler->removeEventListener(listener);
+}
+
 @end

React/Fabric/RCTSurfacePresenter.h

@@ -19,6 +19,7 @@ NS_ASSUME_NONNULL_BEGIN
 @class RCTFabricSurface;
 @class RCTImageLoader;
 @class RCTMountingManager;
+@class RCTScheduler;
 
 /**
  * Coordinates presenting of React Native Surfaces and represents application
@@ -53,6 +54,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)unregisterSurface:(RCTFabricSurface *)surface;
 
 @property (readonly) RCTMountingManager *mountingManager;
+@property (readonly, nullable) RCTScheduler *scheduler;
 
 /*
  * Allow callers to initialize a new fabric surface without adding Fabric as a Buck dependency.

React/Fabric/RCTSurfacePresenter.mm

@@ -115,7 +115,7 @@ - (RCTMountingManager *)mountingManager
   return _mountingManager;
 }
 
-- (RCTScheduler *_Nullable)_scheduler
+- (RCTScheduler *_Nullable)scheduler
 {
   std::lock_guard<std::mutex> lock(_schedulerAccessMutex);
   return _scheduler;
@@ -151,15 +151,15 @@ - (void)setRuntimeExecutor:(RuntimeExecutor)runtimeExecutor
 - (void)registerSurface:(RCTFabricSurface *)surface
 {
   [_surfaceRegistry registerSurface:surface];
-  RCTScheduler *scheduler = [self _scheduler];
+  RCTScheduler *scheduler = [self scheduler];
   if (scheduler) {
     [scheduler registerSurface:surface.surfaceHandler];
   }
 }
 
 - (void)unregisterSurface:(RCTFabricSurface *)surface
 {
-  RCTScheduler *scheduler = [self _scheduler];
+  RCTScheduler *scheduler = [self scheduler];
   if (scheduler) {
     [scheduler unregisterSurface:surface.surfaceHandler];
   }
@@ -188,7 +188,7 @@ - (UIView *)findComponentViewWithTag_DO_NOT_USE_DEPRECATED:(NSInteger)tag
 
 - (BOOL)synchronouslyUpdateViewOnUIThread:(NSNumber *)reactTag props:(NSDictionary *)props
 {
-  RCTScheduler *scheduler = [self _scheduler];
+  RCTScheduler *scheduler = [self scheduler];
   if (!scheduler) {
     return NO;
   }
@@ -212,7 +212,7 @@ - (BOOL)synchronouslyUpdateViewOnUIThread:(NSNumber *)reactTag props:(NSDictiona
 
 - (void)setupAnimationDriverWithSurfaceHandler:(facebook::react::SurfaceHandler const &)surfaceHandler
 {
-  [[self _scheduler] setupAnimationDriver:surfaceHandler];
+  [[self scheduler] setupAnimationDriver:surfaceHandler];
 }
 
 - (BOOL)suspend