Fix warnings_checker.dart handling of multitests

tests/language_strong/assignable_expression_test.dart

 // Copyright (c) 2013, 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.
 
 // Test to detect syntactically illegal left-hand-side (assignable)
 // expressions.
 
 class C {
   static var static_field = 0;
 }
 
 var tl_static_var = 0;
 
 main() {
   tl_static_var = 0;
-  (tl_static_var) = 0; //   /// 01: compile-time error
-  (tl_static_var)++; //     /// 02: compile-time error
-  ++(tl_static_var); //     /// 03: compile-time error
+  (tl_static_var) = 0; //   //# 01: compile-time error
+  (tl_static_var)++; //     //# 02: compile-time error
+  ++(tl_static_var); //     //# 03: compile-time error
 
   C.static_field = 0;
-  (C.static_field) = 0; //  /// 11: compile-time error
-  (C.static_field)++; //    /// 12: compile-time error
-  ++(C.static_field); //    /// 13: compile-time error
+  (C.static_field) = 0; //  //# 11: compile-time error
+  (C.static_field)++; //    //# 12: compile-time error
+  ++(C.static_field); //    //# 13: compile-time error
 
   tl_static_var = [1, 2, 3];
   tl_static_var[0] = 0;
   (tl_static_var)[0] = 0;
-  (tl_static_var[0]) = 0; //   /// 21: compile-time error
-  (tl_static_var[0])++; //     /// 22: compile-time error
-  ++(tl_static_var[0]); //     /// 23: compile-time error
+  (tl_static_var[0]) = 0; //   //# 21: compile-time error
+  (tl_static_var[0])++; //     //# 22: compile-time error
+  ++(tl_static_var[0]); //     //# 23: compile-time error
 
   C.static_field = [1, 2, 3];
-  (C.static_field[0]) = 0; //  /// 31: compile-time error
-  (C.static_field[0])++; //    /// 32: compile-time error
-  ++(C.static_field[0]); //    /// 33: compile-time error
+  (C.static_field[0]) = 0; //  //# 31: compile-time error
+  (C.static_field[0])++; //    //# 32: compile-time error
+  ++(C.static_field[0]); //    //# 33: compile-time error
 
   var a = 0;
-  (a) = 0; //  /// 41: compile-time error
-  (a)++; //    /// 42: compile-time error
-  ++(a); //    /// 43: compile-time error
+  (a) = 0; //  //# 41: compile-time error
+  (a)++; //    //# 42: compile-time error
+  ++(a); //    //# 43: compile-time error
 
   // Neat palindrome expression. x is assignable, ((x)) is not.
-  var funcnuf = (x) => ((x))=((x)) <= (x); // /// 50: compile-time error
+  var funcnuf = (x) => ((x))=((x)) <= (x); // //# 50: compile-time error
 }