[turbofan] Port initialization of new.target variable.

src/frames.h

Index: src/frames.h
diff --git a/src/frames.h b/src/frames.h
index 562445a2f1b115f71ed3ea17f97f0452f90afa03..ca3aba441a284240d44d0ac4796675ab3b257124 100644
--- a/src/frames.h
+++ b/src/frames.h
@@ -533,6 +533,10 @@ class JavaScriptFrame: public StandardFrame {
   // Check if this frame is a constructor frame invoked through 'new'.
   bool IsConstructor() const;
 
+  // Returns the original constructor function that was used in the constructor
+  // call to this frame. Note that this is only valid on constructor frames.
+  Object* GetOriginalConstructor() const;
+
   // Check if this frame has "adapted" arguments in the sense that the
   // actual passed arguments are available in an arguments adaptor
   // frame below it on the stack.