Adds the possibility of setting a Code object as the callback of a FunctionTemplate.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 89659dad76a65b821e55861f734cce8021b370d7..08ff889ed6de6452545cee634458946f42099214 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -10352,6 +10352,7 @@ class CallHandlerInfo: public Struct {
  public:
   DECL_ACCESSORS(callback, Object)
   DECL_ACCESSORS(data, Object)
+  DECL_ACCESSORS(fast_handler, Object)
 
   DECLARE_CAST(CallHandlerInfo)
 
@@ -10361,7 +10362,8 @@ class CallHandlerInfo: public Struct {
 
   static const int kCallbackOffset = HeapObject::kHeaderSize;
   static const int kDataOffset = kCallbackOffset + kPointerSize;
-  static const int kSize = kDataOffset + kPointerSize;
+  static const int kFastHandlerOffset = kDataOffset + kPointerSize;
+  static const int kSize = kFastHandlerOffset + kPointerSize;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(CallHandlerInfo);