[stubs] Properly handle read-only properties in StoreGlobalViaContextStub.

src/property-details.h

Index: src/property-details.h
diff --git a/src/property-details.h b/src/property-details.h
index 791eb524c77c40e9f1230657c2d9d84cfadcb7df..5d95f05e8ac28741c148fa92ab812e3afad6acfc 100644
--- a/src/property-details.h
+++ b/src/property-details.h
@@ -320,6 +320,8 @@ class PropertyDetails BASE_EMBEDDED {
   class KindField : public BitField<PropertyKind, 0, 1> {};
   class LocationField : public BitField<PropertyLocation, 1, 1> {};
   class AttributesField : public BitField<PropertyAttributes, 2, 3> {};
+  static const int kAttributesReadOnlyMask =
+      (READ_ONLY << AttributesField::kShift);
 
   // Bit fields for normalized objects.
   class PropertyCellTypeField : public BitField<PropertyCellType, 5, 2> {};