Fix warnings_checker.dart handling of multitests

tests/language_strong/switch_case_test.dart

Index: tests/language_strong/switch_case_test.dart
diff --git a/tests/language_strong/switch_case_test.dart b/tests/language_strong/switch_case_test.dart
index 8d0b80d5ac248ce41642f2a8717936acc4ecfcdc..2ed1df5b28450c1bd6494e846fc9147307ebf281 100644
--- a/tests/language_strong/switch_case_test.dart
+++ b/tests/language_strong/switch_case_test.dart
@@ -14,7 +14,7 @@ class A {
 class B implements A {
   const B();
 
-  operator ==(o) => true; // /// 00: compile-time error
+  operator ==(o) => true; // //# 00: compile-time error
 }
 
 class C implements A {
@@ -30,18 +30,18 @@ class D implements C {
 
 main() {
   switch (new B()) {
-    case const A.B(): Expect.fail("bad switch"); break; // /// 00: continued
+    case const A.B(): Expect.fail("bad switch"); break; // //# 00: continued
   }
 
   switch (new C()) {
     case const C(): Expect.fail("bad switch"); break;
     case const A.C(): Expect.fail("bad switch"); break;
     case const A.C2(): Expect.fail("bad switch"); break;
-    case const A(): Expect.fail("bad switch"); break; // /// 01: compile-time error
+    case const A(): Expect.fail("bad switch"); break; // //# 01: compile-time error
   }
 
   switch (new A()) {
     case const A(): Expect.fail("bad switch"); break;
-    case const A.B(): Expect.fail("bad switch"); break; // /// 02: compile-time error
+    case const A.B(): Expect.fail("bad switch"); break; // //# 02: compile-time error
   }
 }