Write barrier for storing a code entry, and usage in CompileLazy builtin.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 85b795e9ff627e662572435b7a6cbb92eef25d10..db5f204cf8cea0cb1ac2adfd62c611d5add13877 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -294,6 +294,11 @@ class MacroAssembler: public Assembler {
       PointersToHereCheck pointers_to_here_check_for_value =
           kPointersToHereMaybeInteresting);
 
+  // Notify the garbage collector that we wrote a code entry into a
+  // JSFunction. Only scratch is clobbered by the operation.
+  void RecordWriteCodeEntryField(Register js_function, Register code_entry,
+                                 Register scratch);
+
   void RecordWriteForMap(
       Register object,
       Register map,