Attempt at capturing screenshot on IE if tests time out

tools/capture_screenshot.ps1

+# Copyright (c) 2017, 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.
+
+[Reflection.Assembly]::LoadWithPartialName("System.Drawing")
+function screenshot([Drawing.Rectangle]$bounds, $path) {
+   $bmp = New-Object Drawing.Bitmap $bounds.width, $bounds.height
+   $graphics = [Drawing.Graphics]::FromImage($bmp)
+
+   $graphics.CopyFromScreen(
+       $bounds.Location, [Drawing.Point]::Empty, $bounds.size)
+
+   $bmp.Save($path)
+
+   $graphics.Dispose()
+   $bmp.Dispose()
+}
+
+$bounds = [Drawing.Rectangle]::FromLTRB(0, 0, 2000, 4000)
+screenshot $bounds $args[0]