Adds `DartOptions` to generic method syntax tests.

tests/language/generic_sends_test.dart

 // Copyright (c) 2016, 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.
+//
+// DartOptions=--generic-method-syntax
 
 /// Dart test verifying that the parser can handle certain cases where
 /// grammar ambiguity is resolved in favor of generic sends, not
 /// relational expressions.
 
 library generic_sends_test;
 
 f(arg1, [arg2]) => null;
 g<X, Y>(arg) => null;
 
 main() {
   // Generic invocations.
   f(g<int, String>(3));
   f(g<int, List<String>>(3));
   f(g<int, String>(3), 4);
   f(g<int, List<String>>(3), 4);
 
   // Relational expressions.
   int a = 0, b = 1, c = 2, d = 3;
   f(a < b, c > 3);
   f(a < b, c >> 3);
   f(a < b, c < d >> 3);
 }