Fix missing write barrier in store field stub.

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index 1b8ed3848c2ff1aeb13e5f2c5286b367e2c47ac7..2cfe17b5bedd60de819d6b2b3305b1b57b2f1ced 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -768,9 +768,19 @@ void StubCompiler::GenerateStoreField(MacroAssembler* masm,
   }
 
   if (!transition.is_null()) {
-    // Update the map of the object; no write barrier updating is
-    // needed because the map is never in new space.
-    __ Move(FieldOperand(receiver_reg, HeapObject::kMapOffset), transition);
+    // Update the map of the object.
+    __ Move(scratch, transition);
+    __ movq(FieldOperand(receiver_reg, HeapObject::kMapOffset), scratch);
+
+    // Update the write barrier for the map field and pass the now unused
+    // name_reg as scratch register.
+    __ RecordWriteField(receiver_reg,
+                        HeapObject::kMapOffset,
+                        scratch,
+                        name_reg,
+                        kDontSaveFPRegs,
+                        OMIT_REMEMBERED_SET,
+                        OMIT_SMI_CHECK);
   }
 
   // Adjust for the number of properties stored in the object. Even in the