Remove unused 'receiver' field from generators

src/x64/builtins-x64.cc

Index: src/x64/builtins-x64.cc
diff --git a/src/x64/builtins-x64.cc b/src/x64/builtins-x64.cc
index 9fbade7733a6a33af5dfde09bac750d1662a1dfd..746079ad0aacdecf8ba17532291047e764874aca 100644
--- a/src/x64/builtins-x64.cc
+++ b/src/x64/builtins-x64.cc
@@ -501,8 +501,8 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
   // Pop return address.
   __ PopReturnAddressTo(rax);
 
-  // Push receiver.
-  __ Push(FieldOperand(rbx, JSGeneratorObject::kReceiverOffset));
+  // Push hole for the never-used receiver, similarly to arguments below.
+  __ PushRoot(Heap::kTheHoleValueRootIndex);
 
   // ----------- S t a t e -------------
   //  -- rax    : return address