Switch to downloaded SDK executable, drop executables in testing/bin.

tools/testing/dart/test_suite.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 enumerating and preparing tests.
  *
  * This library includes:
  *
  * - Creating tests by listing all the Dart files in certain directories,
@@ skipping 2369 matching lines @@
       throw "You can't have both $normalDir and $crossDir, we don't know which"
             " binary to use";
     }
     if (crossDir.existsSync()) {
       return cross;
     }
     return normal;
   }
 
   /**
-   * Returns the path to the dart binary checked into the repo, used for
-   * bootstrapping test.dart.
-   */
-  static Path get dartTestExecutable {
-    var path = '$dartDir/tools/testing/bin/'
-        '${Platform.operatingSystem}/dart';
-    if (Platform.operatingSystem == 'windows') {
-      path = '$path.exe';
-    }
-    return new Path(path);
-  }
-
-  /**
    * Gets extra options under [key] passed to the testing script.
    */
   static List<String> getExtraOptions(Map configuration, String key) {
     if (configuration[key] == null) return <String>[];
     return configuration[key]
         .split(" ")
         .map((s) => s.trim())
         .where((s) => s.isNotEmpty)
         .toList();
   }
@@ skipping 74 matching lines @@
       for (var key in PATH_REPLACEMENTS.keys) {
         if (path.startsWith(key)) {
           path = path.replaceFirst(key, PATH_REPLACEMENTS[key]);
           break;
         }
       }
     }
     return path;
   }
 }