[telemetry] Add a webdriver backend with support for IE.

tools/telemetry/telemetry/core/chrome/desktop_browser_backend.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 import logging
 import os
 import subprocess as subprocess
 import shutil
 import sys
 import tempfile
 
@@ skipping 157 matching lines @@
     if self._delete_profile_dir_after_run and \
         self._tmpdir and os.path.exists(self._tmpdir):
       shutil.rmtree(self._tmpdir, ignore_errors=True)
       self._tmpdir = None
 
     if self._tmp_output_file:
       self._tmp_output_file.close()
       self._tmp_output_file = None
 
   def CreateForwarder(self, *port_pairs):
-    return browser_backend.DoNothingForwarder(*port_pairs)
+    return util.DoNothingForwarder(*port_pairs)