Parsing: Make Scope not know about Isolate.

src/preparser.h

Index: src/preparser.h
diff --git a/src/preparser.h b/src/preparser.h
index 3d33dd0bf70b5ef0445e4de7505e1937befb49b9..bb7b40d2c9570e335edd7f250574fcdb07d97054 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -310,8 +310,8 @@ class ParserBase : public Traits {
     DCHECK(scope_type != MODULE_SCOPE || allow_harmony_modules());
     DCHECK((scope_type == FUNCTION_SCOPE && IsValidFunctionKind(kind)) ||
            kind == kNormalFunction);
-    Scope* result = new (zone())
-        Scope(isolate(), zone(), parent, scope_type, ast_value_factory());
+    Scope* result =
+        new (zone()) Scope(zone(), parent, scope_type, ast_value_factory());
     bool uninitialized_this =
         FLAG_experimental_classes && IsSubclassConstructor(kind);
     result->Initialize(uninitialized_this);