Fabric: ShadowTree::getRootShadowNode was removed

Summary: Because it was not idiomatic anyway. There is no point having a pointer to RootShadowNode without any guarantees that it's the current one. Using `commit` method makes this concern explicit.

Reviewed By: sahrens

Differential Revision: D13615363

fbshipit-source-id: f71ffc3c55dbdc69624933eb8b92334ed793c794

ReactCommon/fabric/uimanager/ShadowTree.cpp

@@ -50,11 +50,6 @@ Tag ShadowTree::getSurfaceId() const {
   return surfaceId_;
 }
 
-SharedRootShadowNode ShadowTree::getRootShadowNode() const {
-  std::shared_lock<folly::SharedMutex> lock(commitMutex_);
-  return rootShadowNode_;
-}
-
 bool ShadowTree::commit(
     std::function<UnsharedRootShadowNode(
         const SharedRootShadowNode &oldRootShadowNode)> transaction,

ReactCommon/fabric/uimanager/ShadowTree.h

@@ -54,11 +54,6 @@ class ShadowTree final {
       int attempts = 1,
       int *revision = nullptr) const;
 
-  /*
-   * Returns a root shadow node that represents the last committed three.
-   */
-  SharedRootShadowNode getRootShadowNode() const;
-
 #pragma mark - Delegate
 
   /*

ReactCommon/fabric/uimanager/UIManager.cpp

@@ -100,7 +100,10 @@ LayoutMetrics UIManager::getRelativeLayoutMetrics(
   if (!ancestorShadowNode) {
     shadowTreeRegistry_->visit(
         shadowNode.getRootTag(), [&](const ShadowTree &shadowTree) {
-          ancestorShadowNode = shadowTree.getRootShadowNode().get();
+          shadowTree.commit([&](const SharedRootShadowNode &oldRootShadowNode) {
+            ancestorShadowNode = oldRootShadowNode.get();
+            return nullptr;
+          });
         });
   }