Relax string literal requirements on arguments

pkg/intl/test/message_extraction/part_of_sample_with_messages.dart

 // Copyright (c) 2013, 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.part of sample;
 
 part of sample;
 
 class Person {
   String name;
   String gender;
   Person(this.name, this.gender);
 }
 
 class YouveGotMessages {
 
   // A static message, rather than a standalone function.
   static staticMessage() => Intl.message("This comes from a static method",
       name: 'staticMessage');
 
   // An instance method, rather than a standalone function.
-  method() => Intl.message("This comes from a method", name: 'method');
+  method() => Intl.message("This comes from a method", name: 'method',
+      desc: 'This is a method with a '
+            'long description which spans '
+            'multiple lines.');
 
   // A non-lambda, i.e. not using => syntax, and with an additional statement
   // before the Intl.message call.
   nonLambda() {
     // TODO(alanknight): I'm really not sure that this shouldn't be disallowed.
     var x = 'something';
     return Intl.message("This method is not a lambda", name: 'nonLambda');
   }
 
   plurals(num) => Intl.message("""${Intl.plural(num,
@@ skipping 35 matching lines @@
             other: "${names} sont allés au $place")}',
           female: '${Intl.plural(number,
             one: "$names est allée au $place",
           other: "$names sont allées au $place")}'
         )}''',
        name: "nestedMessage",
        args: [names, number, combinedGender, place]);
     return nestedMessage(names, number, combinedGender, place);
   }
 }