Change test scripts to use Path library in most places, instead of strings.

tools/testing/dart/test_runner.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.
 
 /**
  * Classes and methods for executing tests.
  *
  * This module includes:
  * - Managing parallel execution of tests, including timeout checks.
  * - Evaluating the output of each test as pass/fail/crash/timeout.
@@ skipping 385 matching lines @@
     return false;
   }
 
   bool _didStandardTestFail(List errors, List staticWarnings) {
     bool hasFatalTypeErrors = false;
     int numStaticTypeAnnotations = 0;
     int numCompileTimeAnnotations = 0;
     var isStaticClean = false;
     if (testCase.info != null) {
       var optionsFromFile = testCase.info.optionsFromFile;
-      hasFatalTypeErrors = optionsFromFile['hasFatalTypeErrors'];
+      hasFatalTypeErrors = testCase.info.hasFatalTypeErrors;
       for (Command c in testCase.commands) {
         for (String arg in c.arguments) {
           if (arg == '--fatal-type-errors') {
             hasFatalTypeErrors = true;
             break;
           }
         }
       }
       numStaticTypeAnnotations = optionsFromFile['numStaticTypeAnnotations'];
       numCompileTimeAnnotations = optionsFromFile['numCompileTimeAnnotations'];
@@ skipping 762 matching lines @@
         // the developer doesn't waste his or her time trying to fix a bunch of
         // tests that appear to be broken but were actually just flakes that
         // didn't get retried because there had already been one failure.
         bool allowRetry = _MAX_FAILED_NO_RETRY > _progress.numFailedTests;
         new RunningProcess(test, allowRetry, this).start();
       }
       _numProcesses++;
     }
   }
 }