Fix warnings_checker.dart handling of multitests

tests/language/if_null_behavior_test.dart

 // Copyright (c) 2015, 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.
 
 // Evaluation of an if-null expresion e of the form e1 ?? e2 is equivalent to
 // the evaluation of the expression ((x) => x == null ? e2 : x)(e1).  The
 // static type of e is the least upper bound of the static type of e1 and the
 // static type of e2.
 
 import "package:expect/expect.dart";
@@ skipping 16 matching lines @@
 B nullB() => null;
 C nullC() => null;
 
 noMethod(e) => e is NoSuchMethodError;
 
 main() {
   // Make sure the "none" test fails if "??" is not implemented.  This makes
   // status files easier to maintain.
   var _ = null ?? null;
 
-  Expect.equals(1, 1 ?? 2); /// 01: ok
-  Expect.equals(1, 1 ?? null); /// 02: ok
-  Expect.equals(2, null ?? 2); /// 03: ok
-  Expect.equals(null, null ?? null); /// 04: ok
-  Expect.equals('B', (new B('B') ?? new C('C')).a); /// 05: ok
-  Expect.equals('B', (new B('B') ?? new C('C')).b); /// 06: static type warning
-  Expect.throws(() => (new B('B') ?? new C('C')).c, noMethod); /// 07: static type warning
-  Expect.equals('B', (new B('B') ?? nullC()).a); /// 08: ok
-  Expect.equals('B', (new B('B') ?? nullC()).b); /// 09: static type warning
-  Expect.throws(() => (new B('B') ?? nullC()).c, noMethod); /// 10: static type warning
-  Expect.equals('C', (nullB() ?? new C('C')).a); /// 11: ok
-  Expect.throws(() => (nullB() ?? new C('C')).b, noMethod); /// 12: static type warning
-  Expect.equals('C', (nullB() ?? new C('C')).c); /// 13: static type warning
-  Expect.throws(() => (nullB() ?? nullC()).a, noMethod); /// 14: ok
-  Expect.throws(() => (nullB() ?? nullC()).b, noMethod); /// 15: static type warning
-  Expect.throws(() => (nullB() ?? nullC()).c, noMethod); /// 16: static type warning
+  Expect.equals(1, 1 ?? 2); //# 01: ok
+  Expect.equals(1, 1 ?? null); //# 02: ok
+  Expect.equals(2, null ?? 2); //# 03: ok
+  Expect.equals(null, null ?? null); //# 04: ok
+  Expect.equals('B', (new B('B') ?? new C('C')).a); //# 05: ok
+  Expect.equals('B', (new B('B') ?? new C('C')).b); //# 06: static type warning
+  Expect.throws(() => (new B('B') ?? new C('C')).c, noMethod); //# 07: static type warning
+  Expect.equals('B', (new B('B') ?? nullC()).a); //# 08: ok
+  Expect.equals('B', (new B('B') ?? nullC()).b); //# 09: static type warning
+  Expect.throws(() => (new B('B') ?? nullC()).c, noMethod); //# 10: static type warning
+  Expect.equals('C', (nullB() ?? new C('C')).a); //# 11: ok
+  Expect.throws(() => (nullB() ?? new C('C')).b, noMethod); //# 12: static type warning
+  Expect.equals('C', (nullB() ?? new C('C')).c); //# 13: static type warning
+  Expect.throws(() => (nullB() ?? nullC()).a, noMethod); //# 14: ok
+  Expect.throws(() => (nullB() ?? nullC()).b, noMethod); //# 15: static type warning
+  Expect.throws(() => (nullB() ?? nullC()).c, noMethod); //# 16: static type warning
 }