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

tools/telemetry/telemetry/core/chrome/browser_backend.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.

[dtu, 2013/07/31 01:34:49]

I think the right thing to do is create another folder and put browser_backend
in there, so both chrome and webdriver can inherit from it.

telemetry/core/backends/browser_backend.py
telemetry/core/backends/chrome/chrome_browser_backend.py
telemetry/core/backends/webdriver/webdriver_browser_backend.py

This way, browser_backend is accessible by both, but still kept separate from
the "public" methods in telemetry/core/

It may seem unjustified to do a big rename just to move one file, but I think
we're going to have a lot more things moving from core/chrome/ to there as this
effort progresses.

[chrisgao (Use stgao instead), 2013/07/31 19:05:41]

Thanks, Dave. Will do it in next upload and a separate CL.
Per your suggestion, we'd better to move telemetry/core/webdriver/* to
telemetry/core/backends/webdriver, right?

[dtu, 2013/08/01 00:11:13]

Yep.

 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import urllib2
 import httplib
 import socket
 import json
 import re
 import sys
 
@@ skipping 13 matching lines @@
   pass
 
 class BrowserBackend(object):
   """A base class for browser backends. Provides basic functionality
   once a remote-debugger port has been established."""
 
   WEBPAGEREPLAY_HOST = '127.0.0.1'
 
   def __init__(self, is_content_shell, supports_extensions, options):
     self.browser_type = options.browser_type
+    self.webdriver_based = False

[nduca, 2013/07/30 06:49:45]

why is this needed? This is like having a isCrOS on the browserbackend, which of
course we'd say no to.

[chrisgao (Use stgao instead), 2013/07/31 19:05:41]

Removed.

     self.is_content_shell = is_content_shell
     self._supports_extensions = supports_extensions
     self.options = options
     self._browser = None
     self._port = None
 
     self._inspector_protocol_version = 0
     self._chrome_branch_number = 0
     self._tracing_backend = None
 
@@ skipping 198 matching lines @@
     raise NotImplementedError()
 
   def IsBrowserRunning(self):
     raise NotImplementedError()
 
   def GetStandardOutput(self):
     raise NotImplementedError()
 
   def GetStackTrace(self):
     raise NotImplementedError()
-
-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