clean up surface register / start

Summary:
`RCTSurfaceHostingProxyRootView` surfaces are still automatically started right after the initialization to match `RCTRootView` interface, but `RCTSurfaceHostingView` must be started explicitly now. Also fixed some internal stuff so start and register are clear and distinct.

Background / initial motivation:

One tricky bit - we render the template as part of init`ing the rootView, so we don't know what the surfaceId will be before hand to register the UITemplate. Two possible solutions:

1) Require start be called explicitly after initializing the rootView, and setup the context in between.
2) Do something like "setUITemplateConfigForNextSurface" before creating the rootView, and have some hook when the surfaceId is assigned that associates the surfaceId with that "next" UITemplate stuff before.

(1) seems a lot cleaner, but it requires ever user of rootView to explicitly call start on it - how do you feel about that? Seems like we could also use that start call to decide if the initial render should be synchronous or not? start vs. startSync?

Reviewed By: mdvacca

Differential Revision: D13372914

fbshipit-source-id: 6db297870610e6c231f8a78c0dd74d584cb64910

React/Base/Surface/SurfaceHostingView/RCTSurfaceHostingProxyRootView.mm

@@ -69,6 +69,7 @@ static RCTRootViewSizeFlexibility convertToRootViewSizeFlexibility(RCTSurfaceSiz
 
   if (self = [super initWithBridge:bridge moduleName:moduleName initialProperties:initialProperties sizeMeasureMode:sizeMeasureMode]) {
     self.backgroundColor = [UIColor whiteColor];
+    [super.surface start];
   }
 
   RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");

React/Base/Surface/SurfaceHostingView/RCTSurfaceHostingView.mm

@@ -51,7 +51,6 @@ RCT_NOT_IMPLEMENTED(- (nullable instancetype)initWithCoder:(NSCoder *)coder)
 {
   if (self = [super initWithFrame:CGRectZero]) {
     _surface = surface;
-    [_surface start];
     _sizeMeasureMode = sizeMeasureMode;
 
     _surface.delegate = self;

React/Fabric/RCTSurfacePresenter.h

@@ -38,10 +38,14 @@ NS_ASSUME_NONNULL_BEGIN
 @interface RCTSurfacePresenter (Surface)
 
 /**
- * Surface uses those methods to register itself in the Presenter.
- * Registering initiates running, rendering and mounting processes.
+ * Surface uses these methods to register itself in the Presenter.
  */
 - (void)registerSurface:(RCTFabricSurface *)surface;
+/**
+ * Starting initiates running, rendering and mounting processes.
+ * Should be called after registerSurface and any other surface-specific setup is done
+ */
+- (void)startSurface:(RCTFabricSurface *)surface;
 - (void)unregisterSurface:(RCTFabricSurface *)surface;
 - (void)setProps:(NSDictionary *)props
          surface:(RCTFabricSurface *)surface;

React/Fabric/RCTSurfacePresenter.mm

@@ -99,6 +99,10 @@ using namespace facebook::react;
 - (void)registerSurface:(RCTFabricSurface *)surface
 {
   [_surfaceRegistry registerSurface:surface];
+}
+
+- (void)startSurface:(RCTFabricSurface *)surface
+{
   [self _startSurface:surface];
 }
 

React/Fabric/Surface/RCTFabricSurface.mm

@@ -55,6 +55,8 @@
     _touchHandler = [RCTSurfaceTouchHandler new];
 
     _stage = RCTSurfaceStageSurfaceDidInitialize;
+
+    [_surfacePresenter registerSurface:self];
   }
 
   return self;
@@ -66,7 +68,8 @@
     return NO;
   }
 
-  [_surfacePresenter registerSurface:self];
+  [_surfacePresenter startSurface:self];
+
   return YES;
 }