Re-land FastAccessorBuilder.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index f608cab81cae713159e649334fcadced6933bbb4..8834b49c57beb049407ab95b38aa1d33c4ac272a 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -136,6 +136,10 @@ class CallHandlerHelper;
 class EscapableHandleScope;
 template<typename T> class ReturnValue;
 
+namespace experimental {
+class FastAccessorBuilder;
+}  // namespace experimental
+
 namespace internal {
 class Arguments;
 class Heap;
@@ -4419,7 +4423,8 @@ class V8_EXPORT FunctionTemplate : public Template {
    * the callback cannot be null.
    */
   static Local<FunctionTemplate> NewWithFastHandler(
-      Isolate* isolate, FunctionCallback callback, Local<Value> fast_handler,
+      Isolate* isolate, FunctionCallback callback,
+      experimental::FastAccessorBuilder* fast_handler = nullptr,
       Local<Value> data = Local<Value>(),
       Local<Signature> signature = Local<Signature>(), int length = 0);
 
@@ -4433,9 +4438,9 @@ class V8_EXPORT FunctionTemplate : public Template {
    * callback is called whenever the function created from this
    * FunctionTemplate is called.
    */
-  void SetCallHandler(FunctionCallback callback,
-                      Local<Value> data = Local<Value>(),
-                      Local<Value> fast_handler = Local<Value>());
+  void SetCallHandler(
+      FunctionCallback callback, Local<Value> data = Local<Value>(),
+      experimental::FastAccessorBuilder* fast_handler = nullptr);
 
   /** Set the predefined length property for the FunctionTemplate. */
   void SetLength(int length);