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

tools/telemetry/telemetry/core/browser_finder.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.
 """Finds browsers that can be controlled by telemetry."""
 
 import logging
 
 from telemetry.core.chrome import android_browser_finder
 from telemetry.core.chrome import cros_browser_finder
 from telemetry.core.chrome import desktop_browser_finder
+from telemetry.core.backends.webdriver import webdriver_desktop_browser_finder
 
 BROWSER_FINDERS = [
   desktop_browser_finder,
   android_browser_finder,
-  cros_browser_finder
+  cros_browser_finder,
+  webdriver_desktop_browser_finder
   ]
 
 ALL_BROWSER_TYPES = ','.join([bf.ALL_BROWSER_TYPES for bf in BROWSER_FINDERS])
 
 
 class BrowserTypeRequiredException(Exception):
   pass
 
 class BrowserFinderException(Exception):
   pass
@@ skipping 69 matching lines @@
   improperly set or if an error occurs when finding a browser.
   """
   browsers = []
   for finder in BROWSER_FINDERS:
     browsers.extend(finder.FindAllAvailableBrowsers(options))
 
   type_list = set([browser.browser_type for browser in browsers])
   type_list = list(type_list)
   type_list.sort()
   return type_list