Gardening: update path to capture_screenshot.ps1 script

tools/testing/dart/browser_controller.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.
 library browser;
 
 import "dart:async";
 import "dart:convert" show UTF8, JSON;
 import "dart:core";
 import "dart:io";
 import "dart:math" show min;
@@ skipping 1885 matching lines @@
     return;
   }
 
   print('--------------------------------------------------------------------');
   final String date =
       new DateTime.now().toUtc().toIso8601String().replaceAll(':', '_');
   final screenshotName = 'ie_screenshot_${date}.png';
 
   // The "capture_screen.ps1" script is next to "test.dart" in "tools/"
   final powerShellScript =
-      Platform.script.resolve('capture_screenshot.ps1').toFilePath();
+      Platform.script.resolve('../../capture_screenshot.ps1').toFilePath();
   final screenshotFile =
-      Platform.script.resolve('../$screenshotName').toFilePath();
+      Platform.script.resolve('../../../$screenshotName').toFilePath();
 
   final args = [
     '-ExecutionPolicy',
     'ByPass',
     '-File',
     powerShellScript,
     screenshotFile
   ];
   final ProcessResult result =
       await Process.run('powershell.exe', args, runInShell: true);
@@ skipping 18 matching lines @@
           'exit code: ${result.exitCode}\n'
           'stdout: ${result.stdout}\n'
           'stderr: ${result.stderr}');
     } else {
       print('[$message] Successfully uploaded screenshot to $storageUrl');
     }
     new File(screenshotFile).deleteSync();
   }
   print('--------------------------------------------------------------------');
 }