(early draft) Strict mode - throw exception on assignment to read only property.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index fbfc5fdc25697562730c3ab9ace43c0fb7a914df..de15a7398d7fd8c86242247e778a724153cef8a7 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1361,11 +1361,13 @@ class JSObject: public HeapObject {
 
   MUST_USE_RESULT MaybeObject* SetProperty(String* key,
                                            Object* value,
-                                           PropertyAttributes attributes);
+                                           PropertyAttributes attributes,
+                                           StrictModeFlag strict);
   MUST_USE_RESULT MaybeObject* SetProperty(LookupResult* result,
                                            String* key,
                                            Object* value,
-                                           PropertyAttributes attributes);
+                                           PropertyAttributes attributes,
+                                           StrictModeFlag strict);
   MUST_USE_RESULT MaybeObject* SetPropertyWithFailedAccessCheck(
       LookupResult* result,
       String* name,
@@ -1380,11 +1382,13 @@ class JSObject: public HeapObject {
   MUST_USE_RESULT MaybeObject* SetPropertyWithInterceptor(
       String* name,
       Object* value,
-      PropertyAttributes attributes);
+      PropertyAttributes attributes,
+      StrictModeFlag strict);
   MUST_USE_RESULT MaybeObject* SetPropertyPostInterceptor(
       String* name,
       Object* value,
-      PropertyAttributes attributes);
+      PropertyAttributes attributes,
+      StrictModeFlag strict);
   MUST_USE_RESULT MaybeObject* SetLocalPropertyIgnoreAttributes(
       String* key,
       Object* value,