Move node cloning to YGConfig

Summary:
@public

Encapsulates node cloning within `YGConfig`.
This is necessary for allowing for context-aware cloning functions, which will ultimately allow for removal of weak global JNI references.

Reviewed By: shergin

Differential Revision: D14132608

fbshipit-source-id: 0dec114c8e172b1e34a4b7fd146c43f13c151ade

yoga/YGConfig.cpp

@@ -6,7 +6,7 @@
  */
 #include "YGConfig.h"
 
-YGConfig::YGConfig(YGLogger logger) {
+YGConfig::YGConfig(YGLogger logger) : cloneNodeCallback_{nullptr} {
   logger_.noContext = logger;
   loggerUsesContext_ = false;
 }
@@ -24,3 +24,14 @@ void YGConfig::log(
     logger_.noContext(config, node, logLevel, format, args);
   }
 }
+
+YGNodeRef YGConfig::cloneNode(YGNodeRef node, YGNodeRef owner, int childIndex) {
+  YGNodeRef clone = nullptr;
+  if (cloneNodeCallback_ != nullptr) {
+    clone = cloneNodeCallback_(node, owner, childIndex);
+  }
+  if (clone == nullptr) {
+    clone = YGNodeClone(node);
+  }
+  return clone;
+}