Fabric: Aligning UIManager::startSurface and UIManager::stopSurface signatures

Summary:
In the previous diff, we moved the destruction of a ShadowTree object from `UIManager::stopSurface` method. And the next logical step is to align `UIManager::startSurface` method with the symmetrical approach. Now `stopSurface` accepts a unique pointer to a ShadowTree and `stopSurface` returns it back to the caller; this way we can avoid returning a raw pointer from `startSurface`.

Changelog: [Internal] Fabric-specific internal change.

Reviewed By: sammy-SC

Differential Revision: D27010533

fbshipit-source-id: b9211fb7e67763cc190d6b8c86cb866d20c6693d

ReactCommon/react/renderer/scheduler/SurfaceHandler.cpp

@@ -68,12 +68,16 @@ void SurfaceHandler::start() const noexcept {
       parameters = parameters_;
     }
 
-    link_.shadowTree = &link_.uiManager->startSurface(
+    auto shadowTree = std::make_unique<ShadowTree>(
         parameters.surfaceId,
-        parameters.moduleName,
-        parameters.props,
         parameters.layoutConstraints,
-        parameters.layoutContext);
+        parameters.layoutContext,
+        *link_.uiManager);
+
+    link_.shadowTree = shadowTree.get();
+
+    link_.uiManager->startSurface(
+        std::move(shadowTree), parameters.moduleName, parameters.props);
 
     link_.status = Status::Running;
 

ReactCommon/react/renderer/uimanager/UIManager.cpp

@@ -146,17 +146,13 @@ void UIManager::setIsJSResponder(
   }
 }
 
-ShadowTree const &UIManager::startSurface(
-    SurfaceId surfaceId,
+void UIManager::startSurface(
+    ShadowTree::Unique &&shadowTree,
     std::string const &moduleName,
-    folly::dynamic const &props,
-    LayoutConstraints const &layoutConstraints,
-    LayoutContext const &layoutContext) const {
+    folly::dynamic const &props) const {
   SystraceSection s("UIManager::startSurface");
 
-  auto shadowTree = std::make_unique<ShadowTree>(
-      surfaceId, layoutConstraints, layoutContext, *this);
-  auto shadowTreePointer = shadowTree.get();
+  auto surfaceId = shadowTree->getSurfaceId();
   shadowTreeRegistry_.add(std::move(shadowTree));
 
   runtimeExecutor_([=](jsi::Runtime &runtime) {
@@ -167,8 +163,6 @@ ShadowTree const &UIManager::startSurface(
 
     uiManagerBinding->startSurface(runtime, surfaceId, moduleName, props);
   });
-
-  return *shadowTreePointer;
 }
 
 ShadowTree::Unique UIManager::stopSurface(SurfaceId surfaceId) const {

ReactCommon/react/renderer/uimanager/UIManager.h

@@ -85,12 +85,10 @@ class UIManager final : public ShadowTreeDelegate {
 
 #pragma mark - Surface Start & Stop
 
-  ShadowTree const &startSurface(
-      SurfaceId surfaceId,
+  void startSurface(
+      ShadowTree::Unique &&shadowTree,
       std::string const &moduleName,
-      folly::dynamic const &props,
-      LayoutConstraints const &layoutConstraints,
-      LayoutContext const &layoutContext) const;
+      folly::dynamic const &props) const;
 
   ShadowTree::Unique stopSurface(SurfaceId surfaceId) const;