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

tools/telemetry/telemetry/core/util.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 inspect
 import os
 import socket
 import time
 
 class TimeoutException(Exception):
   pass
@@ skipping 52 matching lines @@
         var _element = _findElement(document, \"""" + text + """\");
         return callback_function(_element);
       })();"""
   return tab.EvaluateJavaScript(code)
 
 class PortPair(object):
   def __init__(self, local_port, remote_port):
     self.local_port = local_port
     self.remote_port = remote_port
 
+class DoNothingForwarder(object):
+  def __init__(self, *port_pairs):
+    self._host_port = port_pairs[0].local_port
+
+  @property
+  def url(self):
+    assert self._host_port
+    return 'http://127.0.0.1:%i' % self._host_port
+
+  def Close(self):
+    self._host_port = None
+
 def GetAvailableLocalPort():
   tmp = socket.socket()
   tmp.bind(('', 0))
   port = tmp.getsockname()[1]
   tmp.close()
 
   return port
 
 def CloseConnections(tab):
   """Closes all TCP sockets held open by the browser."""
   try:
     tab.ExecuteJavaScript("""window.chrome && chrome.benchmarking &&
                              chrome.benchmarking.closeConnections()""")
   except Exception:
     pass