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

src/ast/scopes.h

Index: src/ast/scopes.h
diff --git a/src/ast/scopes.h b/src/ast/scopes.h
index 1c1d5ff4e683041de2713a89442449158cb3ee11..2590f88624b8df38dcf8a7f81dc10806664375e1 100644
--- a/src/ast/scopes.h
+++ b/src/ast/scopes.h
@@ -623,6 +623,7 @@ class DeclarationScope : public Scope {
   void set_asm_function() { asm_module_ = true; }
 
   void DeclareThis(AstValueFactory* ast_value_factory);
+  void DeclareArguments(AstValueFactory* ast_value_factory);
   void DeclareDefaultFunctionVariables(AstValueFactory* ast_value_factory);
 
   // This lookup corresponds to a lookup in the "intermediate" scope sitting