Move test.dart's check for missing test directories from co19 to general framework.

tools/testing/dart/status_file_parser.dart

 // Copyright (c) 2012, 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.
 
 #library("status_file_parser");
 
 #import("dart:io");
 #import("status_expression.dart");
 
 // Possible outcomes of running a test.
@@ skipping 38 matching lines @@
       }
     }
     onDone();
   }
 
   ReadConfigurationInto(statusFilePath, sections, sectionsRead);
 }
 
 void ReadConfigurationInto(path, sections, onDone) {
   File file = new File(path);
-  if (!file.existsSync()) return;  // TODO(whesse): Handle missing file.
+  if (!file.existsSync()) {
+    throw new Exception('Cannot find test status file $path');
+  }
   InputStream file_stream = file.openInputStream();
   StringInputStream lines = new StringInputStream(file_stream);
 
   Section current = new Section.always();
   sections.add(current);
   String prefix = "";
 
   lines.lineHandler = () {
     String line;
     while ((line = lines.readLine()) != null) {
@@ skipping 164 matching lines @@
         }
         regExps[i] = regExp;
       }
       _keyToRegExps[key] = regExps;
     });
 
     _regExpCache = null;
     _preprocessed = true;
   }
 }