Allow lexically declared "arguments" in function scope in sloppy mode.

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index aeef16bb6a34c7b0ad671fd5355d2bcc0c62dfff..56e2a920317f60a4b2821d99e8bf61aaaa76c018 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -4010,6 +4010,10 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
 
     // Parsing the body may change the language mode in our scope.
     language_mode = scope->language_mode();
+    scope->DeclareArguments(ast_value_factory());
+    if (main_scope != scope) {
+      main_scope->DeclareArguments(ast_value_factory());
+    }
 
     // Validate name and parameter names. We can do this only after parsing the
     // function, since the function can declare itself strict.