Fix warnings_checker.dart handling of multitests

tests/language_strong/field_override4_test.dart

Index: tests/language_strong/field_override4_test.dart
diff --git a/tests/language_strong/field_override4_test.dart b/tests/language_strong/field_override4_test.dart
index 6ffd170e8f644842879df941f786a4f954cee1db..69c3b56e9d76372a86a395c9d76de6b21c621c29 100644
--- a/tests/language_strong/field_override4_test.dart
+++ b/tests/language_strong/field_override4_test.dart
@@ -8,10 +8,10 @@
 import "package:expect/expect.dart";
 
 class A {
-  var foo = 42; // /// 00: ok
-  get foo => 42; // /// 01: ok
-  foo() => 42; // /// 02: compile-time error
-  set foo(value) { } // /// 03: ok
+  var foo = 42; // //# 00: ok
+  get foo => 42; // //# 01: ok
+  foo() => 42; // //# 02: compile-time error
+  set foo(value) { } // //# 03: ok
 }
 
 class B extends A {