Fix warnings_checker.dart handling of multitests

tests/language_strong/try_catch_on_syntax_test.dart

 // Copyright (c) 2011, 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.
 
 import "package:expect/expect.dart";
 
 class MyException { }
 
 class MyException1 extends MyException { }
 
 class MyException2 extends MyException { }
 
 void test1() {
   var foo = 0;
   try {
     throw new MyException1();
   }
-  on on MyException2 catch (e) { } /// 02: compile-time error
-  catch MyException2 catch (e) { } /// 03: compile-time error
-  catch catch catch (e) { } /// 04: compile-time error
-  on (e) { } /// 05: compile-time error
-  catch MyException2 catch (e) { } /// 06: compile-time error
+  on on MyException2 catch (e) { } //# 02: compile-time error
+  catch MyException2 catch (e) { } //# 03: compile-time error
+  catch catch catch (e) { } //# 04: compile-time error
+  on (e) { } //# 05: compile-time error
+  catch MyException2 catch (e) { } //# 06: compile-time error
   on MyException2 catch (e) {
     foo = 1;
   } on MyException1 catch (e) {
     foo = 2;
   } on MyException catch (e) {
     foo = 3;
   }
-  on UndefinedClass /// 07: static type warning
+  on UndefinedClass //# 07: static type warning
   catch(e) { foo = 4; }
   Expect.equals(2, foo);
 }
 
 testFinal() {
   try {
     throw "catch this!";
     } catch (e, s) {
       // Test that the error and stack trace variables are final.
-      e = null; // /// 10: runtime error
-      s = null; // /// 11: runtime error
+      e = null; // //# 10: runtime error
+      s = null; // //# 11: runtime error
     }
 }
 
 main() {
   test1();
   testFinal();
 }