ios: expose surfaceForRootTag: up the chain

Summary: The app needs to find the surface by rootTag at some point.

Reviewed By: shergin

Differential Revision: D8391957

fbshipit-source-id: b0bb107b7be882071890afb46de17b50e7ee060d

React/Fabric/RCTSurfacePresenter.h

@@ -9,6 +9,7 @@
 #import <memory>
 
 #import <React/RCTBridge.h>
+#import <React/RCTPrimitives.h>
 #import <fabric/uimanager/FabricUIManager.h>
 
 NS_ASSUME_NONNULL_BEGIN
@@ -36,6 +37,7 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)registerSurface:(RCTFabricSurface *)surface;
 - (void)unregisterSurface:(RCTFabricSurface *)surface;
+- (nullable RCTFabricSurface *)surfaceForRootTag:(ReactTag)rootTag;
 
 /**
  * Measures the Surface with given constraints.
@@ -50,6 +52,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)setMinimumSize:(CGSize)minimumSize
            maximumSize:(CGSize)maximumSize
                surface:(RCTFabricSurface *)surface;
+
 @end
 
 @interface RCTSurfacePresenter (Deprecated)

React/Fabric/RCTSurfacePresenter.mm

@@ -8,16 +8,15 @@
 #import "RCTSurfacePresenter.h"
 
 #import <React/RCTAssert.h>
-#import <React/RCTScheduler.h>
-#import <React/RCTMountingManager.h>
-#import <React/RCTFabricSurface.h>
 #import <React/RCTBridge+Private.h>
-#import <React/RCTMountingManagerDelegate.h>
-#import <React/RCTSurfaceRegistry.h>
 #import <React/RCTComponentViewRegistry.h>
+#import <React/RCTFabricSurface.h>
+#import <React/RCTMountingManager.h>
+#import <React/RCTMountingManagerDelegate.h>
+#import <React/RCTScheduler.h>
+#import <React/RCTSurfaceRegistry.h>
 #import <React/RCTSurfaceView.h>
 #import <React/RCTSurfaceView+Internal.h>
-
 #import <fabric/core/LayoutContext.h>
 #import <fabric/core/LayoutConstraints.h>
 
@@ -83,6 +82,11 @@ using namespace facebook::react;
   [_surfaceRegistry unregisterSurface:surface];
 }
 
+- (RCTFabricSurface *)surfaceForRootTag:(ReactTag)rootTag
+{
+  return [_surfaceRegistry surfaceForRootTag:rootTag];
+}
+
 - (CGSize)sizeThatFitsMinimumSize:(CGSize)minimumSize
                       maximumSize:(CGSize)maximumSize
                           surface:(RCTFabricSurface *)surface