Fix warnings_checker.dart handling of multitests

tests/lib/mirrors/invocation_fuzz_test.dart

 // Copyright (c) 2014, 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.
 
 // This test reflectively enumerates all the methods in the system and tries to
 // invoke them with various basic values (nulls, ints, etc). This may result in
 // Dart exceptions or hangs, but should never result in crashes or JavaScript
 // exceptions.
 
 library test.invoke_natives;
@@ skipping 162 matching lines @@
   // scheduled in the current task. This isn't necessary for the test itself,
   // but is helpful when trying to figure out which function is responsible for
   // a crash.
   testZone.createTimer(Duration.ZERO, doOneTask);
 }
 
 var fuzzArgument;
 
 main() {
   fuzzArgument = null;
-  fuzzArgument = 1; // /// smi: ok
-  fuzzArgument = false; // /// false: ok
-  fuzzArgument = 'string'; // /// string: ok
-  fuzzArgument = new List(0); // /// emptyarray: ok
+  fuzzArgument = 1; // //# smi: ok
+  fuzzArgument = false; // //# false: ok
+  fuzzArgument = 'string'; // //# string: ok
+  fuzzArgument = new List(0); // //# emptyarray: ok
 
   print('Fuzzing with $fuzzArgument');
 
   currentMirrorSystem().libraries.values.forEach(checkLibrary);
 
   var valueObjects =
     [true, false, null, [], {}, dynamic,
      0, 0xEFFFFFF, 0xFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 3.14159, () {},
      "foo", 'blåbærgrød', 'Îñţérñåţîöñåļîžåţîờñ', "\u{1D11E}", #symbol];
   valueObjects.forEach((v) => checkInstance(reflect(v), 'value object'));
 
   uncaughtErrorHandler(self, parent, zone, error, stack) {};
   var zoneSpec =
      new ZoneSpecification(handleUncaughtError: uncaughtErrorHandler);
   testZone = Zone.current.fork(specification: zoneSpec);
   testZone.createTimer(Duration.ZERO, doOneTask);
 }