[parsing]: eval/arguments parameter names are ok in sloppy mode

src/scopes.h

Index: src/scopes.h
diff --git a/src/scopes.h b/src/scopes.h
index 56a7ee97657148e430de38d8344f37cb5d2ec4cf..c3f4f8e2661eb3cade34529ba6df9fa9f8aa14f9 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -467,6 +467,13 @@ class Scope: public ZoneObject {
     return variables_.Lookup(name) != NULL;
   }
 
+  bool IsDeclaredParameter(const AstRawString* name) {
+    // If IsSimpleParameterList is false, duplicate parameters are not allowed,
+    // however `arguments` may be allowed if function is not strict code. Thus,
+    // the assumptions explained above do not hold.
+    return params_.Contains(variables_.Lookup(name));
+  }
+
   // ---------------------------------------------------------------------------
   // Debugging.