Call onRender inline instead of from startRenderCallbackIfNeeded (#51750)

Summary:
Pull Request resolved: #51750

changelog: [internal]

inline call `onRender()` instead of calling it from `startRenderCallbackIfNeeded`. This has identical functionality but allows to use Fantom to test C++ Animated. In Fantom, there is only one thread the existing mechanism in C++ Animated uses thread locals to capture which thread in the UI thread. Therefore, some assumptions are broken. This is just an easy workaround around the problem.

Reviewed By: javache, zeyap

Differential Revision: D75787084

fbshipit-source-id: 8d70ef2d13e4ab14807deb7ca4cb0844980f5901

Author: sammy-SC

packages/react-native/ReactCxxPlatform/react/renderer/animated/NativeAnimatedNodesManager.cpp

@@ -404,6 +404,12 @@ void NativeAnimatedNodesManager::handleAnimatedEvent(
       // `startRenderCallbackIfNeeded` will call platform specific code to
       // register UI tick listener.
       startRenderCallbackIfNeeded();
+      // Calling startOnRenderCallback_ will register a UI tick listener.
+      // The UI ticker listener will not be called until the next frame.
+      // That's why, in case this is called from the UI thread, we need to
+      // proactivelly trigger the animation loop to avoid showing stale
+      // frames.
+      onRender();
     }
   }
 }
@@ -426,14 +432,6 @@ NativeAnimatedNodesManager::ensureEventEmitterListener() noexcept {
 void NativeAnimatedNodesManager::startRenderCallbackIfNeeded() {
   if (startOnRenderCallback_) {
     startOnRenderCallback_([this]() { onRender(); });
-
-    if (isOnRenderThread_) {
-      // Calling startOnRenderCallback_ will register a UI tick listener.
-      // The UI ticker listener will not be called until the next frame.
-      // That's why, in case this is called from the UI thread, we need to
-      // proactivelly trigger the animation loop to avoid showing stale frames.
-      onRender();
-    }
   }
 }