[Telemetry] Factor out common logic between inspector backend lists.

tools/telemetry/telemetry/core/backends/chrome/extension_dict_backend.py

-# Copyright 2013 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 json
-import re
-
-from telemetry.core import extension_page
-from telemetry.core.backends.chrome import inspector_backend
-
-
-class ExtensionNotFoundException(Exception):
-  pass
-
-
-class ExtensionDictBackend(object):
-  def __init__(self, browser_backend):
-    self._browser_backend = browser_backend
-    # Maps extension ids to ExtensionPage objects.
-    self._extension_dict = {}
-
-  def __getitem__(self, extension_id):
-    extension_object = self._extension_dict.get(extension_id)
-    if not extension_object:
-      extension_object = self._CreateExtensionObject(extension_id)
-      assert extension_object
-      self._extension_dict[extension_id] = extension_object
-    return extension_object
-
-  def __contains__(self, extension_id):
-    return extension_id in self.GetExtensionIds()
-
-  @staticmethod
-  def _ExtractExtensionId(url):
-    m = re.match(r"(chrome-extension://)([^/]+)", url)
-    assert m
-    return m.group(2)
-
-  @staticmethod
-  def _GetExtensionId(extension_info):
-    if 'url' not in extension_info:
-      return None
-    return ExtensionDictBackend._ExtractExtensionId(extension_info['url'])
-
-  def _CreateExtensionObject(self, extension_id):
-    extension_info = self._FindExtensionInfo(extension_id)
-    if not extension_info or not 'webSocketDebuggerUrl' in extension_info:
-      raise ExtensionNotFoundException()
-    return extension_page.ExtensionPage(
-        extension_id,
-        extension_info['url'],
-        self._CreateInspectorBackendForDebuggerUrl(
-            extension_info['webSocketDebuggerUrl']))
-
-  def _CreateInspectorBackendForDebuggerUrl(self, debugger_url):
-    return inspector_backend.InspectorBackend(self._browser_backend.browser,
-                                              self._browser_backend,
-                                              debugger_url)
-
-  def _FindExtensionInfo(self, extension_id):
-    for extension_info in self.GetExtensionInfoList():
-      if self._GetExtensionId(extension_info) == extension_id:
-        return extension_info
-    return None
-
-  def GetExtensionInfoList(self, timeout=None):
-    data = self._browser_backend.Request('', timeout=timeout)
-    return self._FilterExtensions(json.loads(data))
-
-  def _FilterExtensions(self, all_pages):
-    return [page_info for page_info in all_pages
-            if page_info['url'].startswith('chrome-extension://')]
-
-  def GetExtensionIds(self):
-    return map(self._GetExtensionId, self.GetExtensionInfoList())