Telemetry support for extensions.

* Browser has new properties supports_extensions and extensions (of type ExtensionDict)
* BrowserBackend ctor takes additional arg supports_extensions. 
* BrowserBackend has new properties supports_extensions and extension_dict_backend (of type ExtensionDictBackend)
* BrowserBackend._WaitForBrowserToComeUp waits for all extensions to load and be interactive.
* BrowserBackend.ExtensionsNotSupportedException is raised for android browser and content shell.
* Add class ExtensionToLoad which is a wrapper for an extension_path.
* Add extension_to_load (of type ExtensionToLoad) to BrowserOptions.
* Add SupportsOptions to PossibleBrowser, to test extensions support. Returns False for android and content_shell when BrowserOptions.extensions_to_load is not empty 
* Add ExtensionPage which derives from WebContents
* Add ExtensionDictBackend which is a dictionary of ExtensionPage instances with extension ids as keys.
* Add ExtensionDict which passes through to ExtensionDictBackend, except it uses ExtensionToLoad instances as keys.
* Import crx_id for determining extension id from extension path.
* Simple extension manifest.json and background.js for unit tests.
* Unit tests for single and multiple extensions.

BUG=169954
TEST=browser test.
Review URL: https://codereview.chromium.org/11882033

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182316 0039d316-1c4b-4281-b951-d872f2087c98

19 files changed, 340 insertions, 21 deletions

diff --git a/tools/telemetry/telemetry/android_browser_backend.py b/tools/telemetry/telemetry/android_browser_backend.py
index 6e2e76a..290e71d 100644
--- a/tools/telemetry/telemetry/android_browser_backend.py
+++ b/tools/telemetry/telemetry/android_browser_backend.py
@@ -17,9 +17,14 @@ from telemetry import browser_gone_exception
 class AndroidBrowserBackend(browser_backend.BrowserBackend):
   """The backend for controlling a browser instance running on Android.
   """
-  def __init__(self, options, adb, package,
-               is_content_shell, cmdline_file, activity, devtools_remote_port):
-    super(AndroidBrowserBackend, self).__init__(is_content_shell, options)
+  def __init__(self, options, adb, package, is_content_shell,
+               cmdline_file, activity, devtools_remote_port):
+    super(AndroidBrowserBackend, self).__init__(
+        is_content_shell=is_content_shell,
+        supports_extensions=False, options=options)
+    if len(options.extensions_to_load) > 0:
+      raise browser_backend.ExtensionsNotSupportedException(
+          'Android browser does not support extensions.')
     # Initialize fields so that an explosion during init doesn't break in Close.
     self._options = options
     self._adb = adb
diff --git a/tools/telemetry/telemetry/android_browser_finder.py b/tools/telemetry/telemetry/android_browser_finder.py
index 37c0b99..da85327 100644
--- a/tools/telemetry/telemetry/android_browser_finder.py
+++ b/tools/telemetry/telemetry/android_browser_finder.py
@@ -44,8 +44,7 @@ CONTENT_SHELL_DEVTOOLS_REMOTE_PORT = (
 class PossibleAndroidBrowser(possible_browser.PossibleBrowser):
   """A launchable android browser instance."""
   def __init__(self, browser_type, options, *args):
-    super(PossibleAndroidBrowser, self).__init__(
-        browser_type, options)
+    super(PossibleAndroidBrowser, self).__init__(browser_type, options)
     self._args = args
 
   def __repr__(self):
@@ -61,6 +60,11 @@ class PossibleAndroidBrowser(possible_browser.PossibleBrowser):
     backend.SetBrowser(b)
     return b
 
+  def SupportsOptions(self, options):
+    if len(options.extensions_to_load) != 0:
+      return False
+    return True
+
 def FindAllAvailableBrowsers(options, logging=real_logging):
   """Finds all the desktop browsers available on this machine."""
   if not adb_commands.IsAndroidSupported():
diff --git a/tools/telemetry/telemetry/browser.py b/tools/telemetry/telemetry/browser.py
index 25591e6..e336884 100644
--- a/tools/telemetry/telemetry/browser.py
+++ b/tools/telemetry/telemetry/browser.py
@@ -3,13 +3,14 @@
 # found in the LICENSE file.
 import os
 
+from telemetry import browser_backend
 from telemetry import browser_credentials
+from telemetry import extension_dict
 from telemetry import tab_list
 from telemetry import temporary_http_server
 from telemetry import wpr_modes
 from telemetry import wpr_server
 
-
 class Browser(object):
   """A running browser instance that can be controlled in a limited way.
 
@@ -21,12 +22,16 @@ class Browser(object):
     with browser_to_create.Create() as browser:
       ... do all your operations on browser here
   """
-  def __init__(self, browser_backend, platform):
-    self._browser_backend = browser_backend
+  def __init__(self, backend, platform):
+    self._browser_backend = backend
     self._http_server = None
     self._wpr_server = None
     self._platform = platform
-    self._tabs = tab_list.TabList(browser_backend.tab_list_backend)
+    self._tabs = tab_list.TabList(backend.tab_list_backend)
+    self._extensions = None
+    if backend.supports_extensions:
+      self._extensions = extension_dict.ExtensionDict(
+          backend.extension_dict_backend)
     self.credentials = browser_credentials.BrowserCredentials()
 
   def __enter__(self):
@@ -49,6 +54,10 @@ class Browser(object):
     return self._browser_backend.is_content_shell
 
   @property
+  def supports_extensions(self):
+    return self._browser_backend.supports_extensions
+
+  @property
   def supports_tab_control(self):
     return self._browser_backend.supports_tab_control
 
@@ -57,6 +66,14 @@ class Browser(object):
     return self._tabs
 
   @property
+  def extensions(self):
+    """Returns the extension dictionary if it exists."""
+    if not self.supports_extensions:
+      raise browser_backend.ExtensionsNotSupportedException(
+          'Extensions not supported')
+    return self._extensions
+
+  @property
   def supports_tracing(self):
     return self._browser_backend.supports_tracing
 
diff --git a/tools/telemetry/telemetry/browser_backend.py b/tools/telemetry/telemetry/browser_backend.py
index 7c7c685..374c867 100644
--- a/tools/telemetry/telemetry/browser_backend.py
+++ b/tools/telemetry/telemetry/browser_backend.py
@@ -10,6 +10,7 @@ import re
 import sys
 
 from telemetry import browser_gone_exception
+from telemetry import extension_dict_backend
 from telemetry import options_for_unittests
 from telemetry import tab_list_backend
 from telemetry import tracing_backend
@@ -18,15 +19,19 @@ from telemetry import util
 from telemetry import wpr_modes
 from telemetry import wpr_server
 
+class ExtensionsNotSupportedException(Exception):
+  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, options):
+  def __init__(self, is_content_shell, supports_extensions, options):
     self.browser_type = options.browser_type
     self.is_content_shell = is_content_shell
+    self._supports_extensions = supports_extensions
     self.options = options
     self._browser = None
     self._port = None
@@ -47,6 +52,10 @@ class BrowserBackend(object):
                        'such as about:flags settings, cookies, and '
                        'extensions.\n')
     self._tab_list_backend = tab_list_backend.TabListBackend(self)
+    self._extension_dict_backend = None
+    if supports_extensions:
+      self._extension_dict_backend = \
+          extension_dict_backend.ExtensionDictBackend(self)
 
   def SetBrowser(self, browser):
     self._browser = browser
@@ -57,9 +66,18 @@ class BrowserBackend(object):
     return self._browser
 
   @property
+  def supports_extensions(self):
+    """True if this browser backend supports extensions."""
+    return self._supports_extensions
+
+  @property
   def tab_list_backend(self):
     return self._tab_list_backend
 
+  @property
+  def extension_dict_backend(self):
+    return self._extension_dict_backend
+
   def GetBrowserStartupArgs(self):
     args = []
     args.extend(self.options.extra_browser_args)
@@ -73,6 +91,12 @@ class BrowserBackend(object):
           self.webpagereplay_remote_https_port))
     args.extend(user_agent.GetChromeUserAgentArgumentFromType(
         self.options.browser_user_agent_type))
+
+    extensions = ','.join(
+        [extension.path for extension in self.options.extensions_to_load])
+    if len(self.options.extensions_to_load) > 0:
+      args.append('--load-extension=%s' % extensions)
+
     return args
 
   @property
@@ -92,6 +116,17 @@ class BrowserBackend(object):
     except util.TimeoutException:
       raise browser_gone_exception.BrowserGoneException()
 
+    def AllExtensionsLoaded():
+      for e in self.options.extensions_to_load:
+        extension_id = e.extension_id()
+        if not extension_id in self._extension_dict_backend:
+          return False
+        extension_object = self._extension_dict_backend[extension_id]
+        extension_object.WaitForDocumentReadyStateToBeInteractiveOrBetter()
+      return True
+    if self._supports_extensions:
+      util.WaitFor(AllExtensionsLoaded, timeout=30)
+
   def _PostBrowserStartupInitialization(self):
     # Detect version information.
     data = self.Request('version')
diff --git a/tools/telemetry/telemetry/browser_finder.py b/tools/telemetry/telemetry/browser_finder.py
index afc7930..8ec6c3a 100644
--- a/tools/telemetry/telemetry/browser_finder.py
+++ b/tools/telemetry/telemetry/browser_finder.py
@@ -53,7 +53,7 @@ def FindBrowser(options):
       return None
 
   matching_browsers = [b for b in browsers
-                       if b.browser_type == options.browser_type]
+      if b.browser_type == options.browser_type and b.SupportsOptions(options)]
 
   if len(matching_browsers) == 1:
     return matching_browsers[0]
diff --git a/tools/telemetry/telemetry/browser_options.py b/tools/telemetry/telemetry/browser_options.py
index 631499c..cb714e8 100644
--- a/tools/telemetry/telemetry/browser_options.py
+++ b/tools/telemetry/telemetry/browser_options.py
@@ -26,6 +26,7 @@ class BrowserOptions(optparse.Values):
     self.extra_browser_args = []
     self.extra_wpr_args = []
     self.show_stdout = False
+    self.extensions_to_load = []
 
     self.cros_remote = None
     self.wpr_mode = wpr_modes.WPR_OFF
diff --git a/tools/telemetry/telemetry/cros_browser_backend.py b/tools/telemetry/telemetry/cros_browser_backend.py
index bdb73fc..28b3bce 100644
--- a/tools/telemetry/telemetry/cros_browser_backend.py
+++ b/tools/telemetry/telemetry/cros_browser_backend.py
@@ -9,11 +9,11 @@ from telemetry import browser_backend
 from telemetry import util
 
 class CrOSBrowserBackend(browser_backend.BrowserBackend):
-  def __init__(self, browser_type, options, is_content_shell, cri):
-    super(CrOSBrowserBackend, self).__init__(is_content_shell, options)
+  def __init__(self, browser_type, options, cri):
+    super(CrOSBrowserBackend, self).__init__(is_content_shell=False,
+        supports_extensions=True, options=options)
     # Initialize fields so that an explosion during init doesn't break in Close.
     self._options = options
-    assert not is_content_shell
     self._cri = cri
     self._browser_type = browser_type
 
diff --git a/tools/telemetry/telemetry/cros_browser_finder.py b/tools/telemetry/telemetry/cros_browser_finder.py
index f9b5847..593d0b9 100644
--- a/tools/telemetry/telemetry/cros_browser_finder.py
+++ b/tools/telemetry/telemetry/cros_browser_finder.py
@@ -16,10 +16,9 @@ ALL_BROWSER_TYPES = ','.join([
     ])
 
 class PossibleCrOSBrowser(possible_browser.PossibleBrowser):
-  """A launchable android browser instance."""
+  """A launchable chromeos browser instance."""
   def __init__(self, browser_type, options, *args):
-    super(PossibleCrOSBrowser, self).__init__(
-        browser_type, options)
+    super(PossibleCrOSBrowser, self).__init__(browser_type, options)
     self._args = args
 
   def __repr__(self):
@@ -32,6 +31,9 @@ class PossibleCrOSBrowser(possible_browser.PossibleBrowser):
     backend.SetBrowser(b)
     return b
 
+  def SupportsOptions(self, options):
+    return True
+
 def FindAllAvailableBrowsers(options):
   """Finds all the desktop browsers available on this machine."""
   if options.cros_remote == None:
@@ -75,4 +77,4 @@ def FindAllAvailableBrowsers(options):
   if not cri.FileExistsOnDevice('/opt/google/chrome/chrome'):
     logging.warn('Could not find a chrome on ' % cri.hostname)
 
-  return [PossibleCrOSBrowser('cros-chrome', options, False, cri)]
+  return [PossibleCrOSBrowser('cros-chrome', options, cri)]
diff --git a/tools/telemetry/telemetry/crx_id.py b/tools/telemetry/telemetry/crx_id.py
new file mode 100644
index 0000000..2e637da
--- /dev/null
+++ b/tools/telemetry/telemetry/crx_id.py
@@ -0,0 +1,16 @@
+# 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.
+from __future__ import absolute_import
+
+import os
+import sys
+
+def __init__():
+  path = os.path.abspath(os.path.join(os.path.dirname(__file__), '..', '..'))
+  sys.path.append(path)
+
+__init__()
+
+from crx_id import crx_id # pylint: disable=F0401
+GetCRXAppID = crx_id.GetCRXAppID
diff --git a/tools/telemetry/telemetry/desktop_browser_backend.py b/tools/telemetry/telemetry/desktop_browser_backend.py
index a0e3d45..cb4d7c92 100644
--- a/tools/telemetry/telemetry/desktop_browser_backend.py
+++ b/tools/telemetry/telemetry/desktop_browser_backend.py
@@ -14,7 +14,9 @@ class DesktopBrowserBackend(browser_backend.BrowserBackend):
   Mac or Windows.
   """
   def __init__(self, options, executable, is_content_shell):
-    super(DesktopBrowserBackend, self).__init__(is_content_shell, options)
+    super(DesktopBrowserBackend, self).__init__(
+        is_content_shell=is_content_shell,
+        supports_extensions=not is_content_shell, options=options)
 
     # Initialize fields so that an explosion during init doesn't break in Close.
     self._proc = None
@@ -25,6 +27,10 @@ class DesktopBrowserBackend(browser_backend.BrowserBackend):
     if not self._executable:
       raise Exception('Cannot create browser, no executable found!')
 
+    if len(options.extensions_to_load) > 0 and is_content_shell:
+      raise browser_backend.ExtensionsNotSupportedException(
+          'Content shell does not support extensions.')
+
     self._port = util.GetAvailableLocalPort()
 
     args = [self._executable]
diff --git a/tools/telemetry/telemetry/desktop_browser_finder.py b/tools/telemetry/telemetry/desktop_browser_finder.py
index 0264a41..2f2243d 100644
--- a/tools/telemetry/telemetry/desktop_browser_finder.py
+++ b/tools/telemetry/telemetry/desktop_browser_finder.py
@@ -40,6 +40,11 @@ class PossibleDesktopBrowser(possible_browser.PossibleBrowser):
     backend.SetBrowser(b)
     return b
 
+  def SupportsOptions(self, options):
+    if (len(options.extensions_to_load) != 0) and self._is_content_shell:
+      return False
+    return True
+
 def FindAllAvailableBrowsers(options):
   """Finds all the desktop browsers available on this machine."""
   browsers = []
@@ -122,8 +127,7 @@ def FindAllAvailableBrowsers(options):
       pass
     if found:
       browsers.append(
-          PossibleDesktopBrowser('system', options,
-                                 'google-chrome', False))
+          PossibleDesktopBrowser('system', options, 'google-chrome', False))
 
   # Win32-specific options.
   if sys.platform.startswith('win'):
diff --git a/tools/telemetry/telemetry/extension_dict.py b/tools/telemetry/telemetry/extension_dict.py
new file mode 100644
index 0000000..5f84af7
--- /dev/null
+++ b/tools/telemetry/telemetry/extension_dict.py
@@ -0,0 +1,26 @@
+# 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.
+
+from telemetry import extension_to_load
+
+class ExtensionDict(object):
+  """Dictionary of ExtensionPage instances, with extension_id as key"""
+
+  def __init__(self, extension_dict_backend):
+    self._extension_dict_backend = extension_dict_backend
+
+  def __getitem__(self, load_extension):
+    """Given an ExtensionToLoad instance, returns the corresponding
+    ExtensionPage instance."""
+    if not isinstance(load_extension, extension_to_load.ExtensionToLoad):
+      raise Exception("Input param must be of type ExtensionToLoad")
+    return self._extension_dict_backend.__getitem__(
+        load_extension.extension_id())
+
+  def __contains__(self, load_extension):
+    """Checks if this ExtensionToLoad instance has been loaded"""
+    if not isinstance(load_extension, extension_to_load.ExtensionToLoad):
+      raise Exception("Input param must be of type ExtensionToLoad")
+    return self._extension_dict_backend.__contains__(
+        load_extension.extension_id())
diff --git a/tools/telemetry/telemetry/extension_dict_backend.py b/tools/telemetry/telemetry/extension_dict_backend.py
new file mode 100644
index 0000000..22f686f
--- /dev/null
+++ b/tools/telemetry/telemetry/extension_dict_backend.py
@@ -0,0 +1,81 @@
+# 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 httplib
+import json
+import re
+import socket
+import urllib2
+import weakref
+
+from telemetry import browser_gone_exception
+from telemetry import extension_page
+from telemetry import inspector_backend
+
+class BrowserConnectionGoneException(
+    browser_gone_exception.BrowserGoneException):
+  pass
+
+class ExtensionDictBackend(object):
+  def __init__(self, browser_backend):
+    self._browser_backend = browser_backend
+    # Maps extension ids to ExtensionPage objects.
+    self._extension_dict = weakref.WeakValueDictionary()
+
+  def __getitem__(self, extension_id):
+    extension_object = self._extension_dict.get(extension_id)
+    if not extension_object:
+      extension_object = self._CreateExtensionObject(extension_id)
+      if 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:
+      return None
+    return extension_page.ExtensionPage(
+        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):
+    try:
+      data = self._browser_backend.Request('', timeout=timeout)
+      return self._FilterExtensions(json.loads(data))
+    except (socket.error, httplib.BadStatusLine, urllib2.URLError):
+      if not self._browser_backend.IsBrowserRunning():
+        raise browser_gone_exception.BrowserGoneException()
+      raise BrowserConnectionGoneException()
+
+  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())
diff --git a/tools/telemetry/telemetry/extension_page.py b/tools/telemetry/telemetry/extension_page.py
new file mode 100644
index 0000000..59ed2fb
--- /dev/null
+++ b/tools/telemetry/telemetry/extension_page.py
@@ -0,0 +1,12 @@
+# 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.
+from telemetry import web_contents
+
+class ExtensionPage(web_contents.WebContents):
+  """Represents a an extension page in the browser"""
+  def __init__(self, inspector_backend):
+    super(ExtensionPage, self).__init__(inspector_backend)
+
+  def __del__(self):
+    super(ExtensionPage, self).__del__()
diff --git a/tools/telemetry/telemetry/extension_to_load.py b/tools/telemetry/telemetry/extension_to_load.py
new file mode 100644
index 0000000..608156d
--- /dev/null
+++ b/tools/telemetry/telemetry/extension_to_load.py
@@ -0,0 +1,15 @@
+# Copyright (c) 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 os
+
+from telemetry import crx_id
+
+class ExtensionToLoad(object):
+  def __init__(self, path):
+    if not os.path.isdir(path):
+      raise Exception('Extension path not a directory %s' % path)
+    self.path = path
+
+  def extension_id(self):
+    return crx_id.GetCRXAppID(os.path.abspath(self.path))
diff --git a/tools/telemetry/telemetry/extension_unittest.py b/tools/telemetry/telemetry/extension_unittest.py
new file mode 100644
index 0000000..f0578229
--- /dev/null
+++ b/tools/telemetry/telemetry/extension_unittest.py
@@ -0,0 +1,74 @@
+# 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 os
+import shutil
+import tempfile
+import unittest
+
+from telemetry import browser_finder
+from telemetry import extension_to_load
+from telemetry import options_for_unittests
+
+class ExtensionTest(unittest.TestCase):
+  def testExtension(self):
+    extension_path = os.path.join(os.path.dirname(__file__),
+        '..', 'unittest_data', 'simple_extension')
+    load_extension = extension_to_load.ExtensionToLoad(extension_path)
+
+    options = options_for_unittests.GetCopy()
+    options.extensions_to_load = [load_extension]
+    browser_to_create = browser_finder.FindBrowser(options)
+    if not browser_to_create:
+      # Could not find a browser that supports extensions.
+      return
+
+    with browser_to_create.Create() as b:
+      extension = b.extensions[load_extension]
+      assert extension
+      extension.ExecuteJavaScript("setTestVar('abcdef')")
+      self.assertEquals('abcdef', extension.EvaluateJavaScript("_testVar"))
+
+class MultipleExtensionTest(unittest.TestCase):
+  def setUp(self):
+    """ Copy the manifest and background.js files of simple_extension to a
+    number of temporary directories to load as extensions"""
+    self._extension_dirs = [tempfile.mkdtemp()
+                            for i in range(3)] # pylint: disable=W0612
+    src_extension_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
+        '..', 'unittest_data', 'simple_extension'))
+    manifest_path = os.path.join(src_extension_dir, 'manifest.json')
+    script_path = os.path.join(src_extension_dir, 'background.js')
+    for d in self._extension_dirs:
+      shutil.copy(manifest_path, d)
+      shutil.copy(script_path, d)
+    self._extensions_to_load = [extension_to_load.ExtensionToLoad(d)
+                                for d in self._extension_dirs]
+    options = options_for_unittests.GetCopy()
+    options.extensions_to_load = self._extensions_to_load
+    browser_to_create = browser_finder.FindBrowser(options)
+    self._browser = None
+    # May not find a browser that supports extensions.
+    if browser_to_create:
+      self._browser = browser_to_create.Create()
+
+  def tearDown(self):
+    if self._browser:
+      self._browser.Close()
+    for d in self._extension_dirs:
+      shutil.rmtree(d)
+
+  def testMultipleExtensions(self):
+    if not self._browser:
+      return
+
+    # Test contains.
+    loaded_extensions = filter(lambda e: e in self._browser.extensions,
+                               self._extensions_to_load)
+    self.assertEqual(len(loaded_extensions), len(self._extensions_to_load))
+
+    for load_extension in self._extensions_to_load:
+      extension = self._browser.extensions[load_extension]
+      assert extension
+      extension.ExecuteJavaScript("setTestVar('abcdef')")
+      self.assertEquals('abcdef', extension.EvaluateJavaScript("_testVar"))
diff --git a/tools/telemetry/telemetry/possible_browser.py b/tools/telemetry/telemetry/possible_browser.py
index 2cb995f..13772af 100644
--- a/tools/telemetry/telemetry/possible_browser.py
+++ b/tools/telemetry/telemetry/possible_browser.py
@@ -20,3 +20,7 @@ class PossibleBrowser(object):
 
   def Create(self):
     raise NotImplementedError()
+
+  def SupportsOptions(self, options):
+    """Tests for extension support."""
+    raise NotImplementedError()
diff --git a/tools/telemetry/unittest_data/simple_extension/background.js b/tools/telemetry/unittest_data/simple_extension/background.js
new file mode 100644
index 0000000..28b5760
--- /dev/null
+++ b/tools/telemetry/unittest_data/simple_extension/background.js
@@ -0,0 +1,8 @@
+// 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.
+
+var _testVar;
+function setTestVar(x) {
+  _testVar = x;
+}
diff --git a/tools/telemetry/unittest_data/simple_extension/manifest.json b/tools/telemetry/unittest_data/simple_extension/manifest.json
new file mode 100644
index 0000000..d4bb6a3
--- /dev/null
+++ b/tools/telemetry/unittest_data/simple_extension/manifest.json
@@ -0,0 +1,9 @@
+{
+  "description": "Simple test extension which has just a background script",
+  "name": "Simple Telemetry Test Extension",
+  "background": {
+    "scripts": ["background.js"]
+  },
+  "manifest_version": 2,
+  "version": "0.1"
+}