Fix warnings_checker.dart handling of multitests

tests/language/if_null_precedence_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.
 
 // Verify that '??' binds tighter than '?:' and less tightly than '||'.
 
 import "package:expect/expect.dart";
 
 assertionError(e) => e is AssertionError;
 
 // Determine whether the VM is running in checked mode.
 bool get checkedMode {
   try {
     var x = 'foo';
     int y = x;
     return false;
   } catch (_) {
     return true;
   }
 }
 
 main() {
   // Make sure the "none" test fails if "??" is not implemented.  This makes
   // status files easier to maintain.
   var _ = null ?? null;
 
   // "a ?? b ?? c" should be legal, and should evaluate to the first non-null
   // value (or null if there are no non-null values).
-  Expect.equals(1, 1 ?? 2 ?? 3); /// 01: ok
-  Expect.equals(2, null ?? 2 ?? 3); /// 02: ok
-  Expect.equals(3, null ?? null ?? 3); /// 03: ok
-  Expect.equals(null, null ?? null ?? null); /// 04: ok
+  Expect.equals(1, 1 ?? 2 ?? 3); //# 01: ok
+  Expect.equals(2, null ?? 2 ?? 3); //# 02: ok
+  Expect.equals(3, null ?? null ?? 3); //# 03: ok
+  Expect.equals(null, null ?? null ?? null); //# 04: ok
 
   // "a ?? b ? c : d" should parse as "(a ?? b) ? c : d", therefore provided
   // that a is true, b need not be a bool.  An incorrect parse of
   // "a ?? (b ? c : d)" would require b to be a bool to avoid a static type
   // warning.
-  Expect.equals(2, true ?? 1 ? 2 : 3); /// 05: ok
+  Expect.equals(2, true ?? 1 ? 2 : 3); //# 05: ok
 
   // "a ?? b || c" should parse as "a ?? (b || c)", therefore it's a static
   // type warning if b doesn't have type bool.  An incorrect parse of
   // "(a ?? b) || c" would allow b to have any type provided that a is bool.
-  Expect.equals(false, false ?? 1 || true); /// 06: static type warning
+  Expect.equals(false, false ?? 1 || true); //# 06: static type warning
 
   // "a || b ?? c" should parse as "(a || b) ?? c", therefore it is a static
   // type warning if b doesn't have type bool.  An incorrect parse of
   // "a || (b ?? c)" would allow b to have any type provided that c is bool.
   if (checkedMode) {
-    Expect.throws(() => false || 1 ?? true, assertionError); /// 07: static type warning
+    Expect.throws(() => false || 1 ?? true, assertionError); //# 07: static type warning
   } else {
-    Expect.equals(false, false || 1 ?? true); //               /// 07: continued
+    Expect.equals(false, false || 1 ?? true); //               //# 07: continued
   }
 
   if (checkedMode) {
     // An incorrect parse of "a || (b ?? c)" would result in no checked-mode
     // error.
-    Expect.throws(() => false || null ?? true, assertionError); /// 08: ok
+    Expect.throws(() => false || null ?? true, assertionError); //# 08: ok
   } else {
     // An incorrect parse of "a || (b ?? c)" would result in c being evaluated.
-    int i = 0; //                                                 /// 08: continued
-    Expect.equals(false, false || null ?? i++ == 0); //           /// 08: continued
-    Expect.equals(0, i); //                                       /// 08: continued
+    int i = 0; //                                                 //# 08: continued
+    Expect.equals(false, false || null ?? i++ == 0); //           //# 08: continued
+    Expect.equals(0, i); //                                       //# 08: continued
   }
 }