[Telemetry] Reduce a websocket connection between telemetry & devtool browser target

telemetry/telemetry/internal/backends/chrome/ios_browser_backend.py

 # Copyright 2014 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 contextlib
 import json
 import logging
 import re
 import urllib2
 
 from telemetry.internal.backends.chrome import chrome_browser_backend
-from telemetry.internal.backends.chrome import system_info_backend
 
 import py_utils
 
 
 class IosBrowserBackend(chrome_browser_backend.ChromeBrowserBackend):
   _DEBUGGER_URL_BUILDER = 'ws://localhost:%i/devtools/page/%i'
   _DEBUGGER_URL_REGEX = r'ws://localhost:(\d+)/devtools/page/(\d+)'
   _DEVICE_LIST_URL = 'http://localhost:9221/json'
 
   def __init__(self, ios_platform_backend, browser_options):
     browser_options.output_profile_path = '.'
     super(IosBrowserBackend, self).__init__(
         ios_platform_backend,
         supports_tab_control=False,
         supports_extensions=False,
         browser_options=browser_options)
     self._webviews = []
     self._port = None
     self._page = None
-    self._system_info_backend = None
     self.UpdateRunningBrowsersInfo()
 
   def UpdateRunningBrowsersInfo(self):
     """ Refresh to match current state of the running browser.
     """
     device_urls = self.GetDeviceUrls()
     urls = self.GetWebSocketDebuggerUrls(device_urls)
     for url in urls:
       m = re.match(self._DEBUGGER_URL_REGEX, url)
       if m:
@@ skipping 53 matching lines @@
         return []
 
     # Find all running UIWebViews.
     debug_urls = []
     for j in data:
       debug_urls.append(j['webSocketDebuggerUrl'])
 
     return debug_urls
 
   def GetSystemInfo(self):
-    if self._system_info_backend is None:
-      self._system_info_backend = system_info_backend.SystemInfoBackend(
-          self._port, self._page)
-    return self._system_info_backend.GetSystemInfo()
+    return None
 
   def IsBrowserRunning(self):
     return bool(self._webviews)
 
   #TODO(baxley): The following were stubbed out to get the sunspider benchmark
   # running. These should be implemented.
   @property
   def browser_directory(self):
     logging.warn('Not implemented')
     return None
@@ skipping 28 matching lines @@
     return None
 
   def GetAllMinidumpPaths(self):
     return None
 
   def GetAllUnsymbolizedMinidumpPaths(self):
     return None
 
   def SymbolizeMinidump(self, minidump_path):
     return None