[runtime] Store constructor function index on primitive maps.

src/arm/builtins-arm.cc

Index: src/arm/builtins-arm.cc
diff --git a/src/arm/builtins-arm.cc b/src/arm/builtins-arm.cc
index 9a68c8dcb336d2f27334e64ceb322e4b8dd5d147..441f57e412a66b845e93582cf0eae2fe979d3954 100644
--- a/src/arm/builtins-arm.cc
+++ b/src/arm/builtins-arm.cc
@@ -442,7 +442,8 @@ static void Generate_JSConstructStubHelper(MacroAssembler* masm,
 
         // Allocate object with a slack.
         __ ldr(r0, FieldMemOperand(r2, Map::kInstanceSizesOffset));
-        __ Ubfx(r0, r0, Map::kInObjectPropertiesByte * kBitsPerByte,
+        __ Ubfx(r0, r0, Map::kInObjectPropertiesOrConstructorFunctionIndexByte *
+                            kBitsPerByte,
                 kBitsPerByte);
         __ ldr(r2, FieldMemOperand(r2, Map::kInstanceAttributesOffset));
         __ Ubfx(r2, r2, Map::kUnusedPropertyFieldsByte * kBitsPerByte,