Emit compile-time errors for conflicting modifiers.

tests/compiler/dart2js/dart_backend_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import "package:expect/expect.dart";
 import 'dart:async';
 import "package:async_helper/async_helper.dart";
 import 'parser_helper.dart';
 import 'mock_compiler.dart';
 import '../../../sdk/lib/_internal/compiler/compiler.dart';
@@ skipping 161 matching lines @@
 testClassWithMethod() {
   testDart2Dart('main(){var a=new A();a.foo();}class A{void foo(){}}');
 }
 
 testExtendsImplements() {
   testDart2Dart('main(){new B<Object>();}'
       'class A<T>{}class B<T> extends A<T>{}');
 }
 
 testVariableDefinitions() {
-  testDart2Dart('main(){final var x,y;final String s;}');
+  testDart2Dart('main(){var x,y;final String s;}');
+  testDart2Dart('main(){final int x,y;final String s;}');
   testDart2Dart('foo(f,g){}main(){foo(1,2);}');
   testDart2Dart('foo(f(arg)){}main(){foo(main);}');
   // A couple of static/finals inside a class.
   testDart2Dart('main(){A.a;A.b;}class A{static const String a="5";'
       'static const String b="4";}');
   // Class member of typedef-ed function type.
   // Maybe typedef should be included in the result too, but it
   // works fine without it.
   testDart2Dart(
     'typedef void foofunc(arg);main(){new A((arg){});}'
@@ skipping 535 matching lines @@
   testStaticAccessIoLib();
   testLocalFunctionPlaceholder();
   testMinification();
   testClosureLocalsMinified();
   testParametersMinified();
   testDeclarationTypePlaceholders();
   testPlatformLibraryMemberNamesAreFixed();
   testConflictsWithCoreLib();
   testUnresolvedNamedConstructor();
 }