Add support for context-aware cloning functions

Summary:
@public

Context-aware cloning functions are an internal Yoga feature that will be used for Yoga’s JNI code.

It will be possible to specify a context when calculating layout, which will be passed on to cloning functions. This will be a private feature.

Reviewed By: SidharthGuglani

Differential Revision: D14149470

fbshipit-source-id: 1d11106e65f9d872d10f191763da001f8d158a61

yoga/YGNode.h

@@ -146,16 +146,16 @@ public:
   // Applies a callback to all children, after cloning them if they are not
   // owned.
   template <typename T>
-  void iterChildrenAfterCloningIfNeeded(T callback) {
+  void iterChildrenAfterCloningIfNeeded(T callback, void* cloneContext) {
     int i = 0;
     for (YGNodeRef& child : children_) {
       if (child->getOwner() != this) {
-        child = config_->cloneNode(child, this, i);
+        child = config_->cloneNode(child, this, i, cloneContext);
         child->setOwner(this);
       }
       i += 1;
 
-      callback(child);
+      callback(child, cloneContext);
     }
   }
 
@@ -335,7 +335,7 @@ public:
   bool removeChild(YGNodeRef child);
   void removeChild(uint32_t index);
 
-  void cloneChildrenIfNeeded();
+  void cloneChildrenIfNeeded(void*);
   void markDirtyAndPropogate();
   float resolveFlexGrow();
   float resolveFlexShrink();