Fix warnings_checker.dart handling of multitests

tests/language_strong/implicit_this_test.dart

Index: tests/language_strong/implicit_this_test.dart
diff --git a/tests/language_strong/implicit_this_test.dart b/tests/language_strong/implicit_this_test.dart
index 490e7e1c2dd133bc9f5b75240ceaf98d1fd015f4..51c2583f538202a857db8bac21fa4a3839f34f92 100644
--- a/tests/language_strong/implicit_this_test.dart
+++ b/tests/language_strong/implicit_this_test.dart
@@ -14,7 +14,7 @@ abstract class Abstract implements Interface {
 
 // This class does not implement "x" either, but it is not marked
 // abstract.
-class SubAbstract1 extends Abstract { } /// 01: static type warning
+class SubAbstract1 extends Abstract { } //# 01: static type warning
 
 // This class is implicitly abstract as it declares an abstract getter
 // method.
@@ -24,7 +24,7 @@ class SubAbstract2 extends Abstract {
 
 // This class does not implement "x" either, but it is not marked
 // abstract.
-class SubSubAbstract2 extends SubAbstract2 { } /// 04: static type warning
+class SubSubAbstract2 extends SubAbstract2 { } //# 04: static type warning
 
 class Concrete extends Abstract {
   get x => 7;
@@ -36,11 +36,11 @@ class SubConcrete extends Concrete {
 }
 
 void main() {
-  var x = new Abstract(); /// 02: runtime error
-  var y = new SubAbstract1(); /// 01: continued
+  var x = new Abstract(); //# 02: runtime error
+  var y = new SubAbstract1(); //# 01: continued
   var z = new SubAbstract2();
-  var a = new SubSubAbstract2(); /// 04: continued
-  Expect.equals(x, x); /// 02: continued
+  var a = new SubSubAbstract2(); //# 04: continued
+  Expect.equals(x, x); //# 02: continued
   Expect.equals('7', new Concrete().toString());
   Expect.equals('42', new SubConcrete(42).toString());
   Expect.equals('7', new SubConcrete(new Concrete()).toString());