Fix warnings_checker.dart handling of multitests

tests/corelib/from_environment_const_type_undefined_test.dart

Index: tests/corelib/from_environment_const_type_undefined_test.dart
diff --git a/tests/corelib/from_environment_const_type_undefined_test.dart b/tests/corelib/from_environment_const_type_undefined_test.dart
index 7cda78fad1ea306e34f807a64ab2a63b06b81487..076fa7e144cfd776117d24b27d3f606b601d2607 100644
--- a/tests/corelib/from_environment_const_type_undefined_test.dart
+++ b/tests/corelib/from_environment_const_type_undefined_test.dart
@@ -7,31 +7,31 @@ import "package:expect/expect.dart";
 class Foo {}
 
 const
-    bool //  /// 01: ok
-    int //   /// 02: static type warning, checked mode compile-time error
-    String /// 03: static type warning, checked mode compile-time error
-    Foo //   /// 04: static type warning, checked mode compile-time error
+    bool //  //# 01: ok
+    int //   //# 02: static type warning, checked mode compile-time error
+    String //# 03: static type warning, checked mode compile-time error
+    Foo //   //# 04: static type warning, checked mode compile-time error
     a = const bool.fromEnvironment('a');
 
 const
-    bool //  /// 05: ok
-    int //   /// 06: static type warning, checked mode compile-time error
-    String /// 07: static type warning, checked mode compile-time error
-    Foo //   /// 08: static type warning, checked mode compile-time error
+    bool //  //# 05: ok
+    int //   //# 06: static type warning, checked mode compile-time error
+    String //# 07: static type warning, checked mode compile-time error
+    Foo //   //# 08: static type warning, checked mode compile-time error
     b = const bool.fromEnvironment('b');
 
 const
-    bool //  /// 09: static type warning
-    int //   /// 10: ok
-    String /// 11: static type warning
-    Foo //   /// 12: static type warning
+    bool //  //# 09: static type warning
+    int //   //# 10: ok
+    String //# 11: static type warning
+    Foo //   //# 12: static type warning
     c = const int.fromEnvironment('c');
 
 const
-    bool //  /// 13: static type warning
-    int //   /// 14: static type warning
-    String /// 15: ok
-    Foo //   /// 16: static type warning
+    bool //  //# 13: static type warning
+    int //   //# 14: static type warning
+    String //# 15: ok
+    Foo //   //# 16: static type warning
     d = const String.fromEnvironment('d');
 
 main() {