Docserver: Add support for viewing docs with a codereview patch applied

chrome/common/extensions/docs/server2/render_servlet.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.
 
 from fnmatch import fnmatch
 import logging
 import mimetypes
 import os
 import traceback
 
@@ skipping 40 matching lines @@
     if path_with_channel.endswith('/'):
       return Response.Redirect(path_with_channel + 'index.html')
 
     channel, path = BranchUtility.SplitChannelNameFromPath(path_with_channel)
 
     if channel == _DEFAULT_CHANNEL:
       return Response.Redirect('/%s' % path)
 
     if channel is None:
       channel = _DEFAULT_CHANNEL
+      base_path = '/'
+    else:
+      base_path = '/%s/' % channel
 
     # AppEngine instances should never need to call out to SVN. That should
     # only ever be done by the cronjobs, which then write the result into
     # DataStore, which is as far as instances look. To enable this, crons can
     # pass a custom (presumably online) ServerInstance into Get().
     #
     # Why? SVN is slow and a bit flaky. Cronjobs failing is annoying but
     # temporary. Instances failing affects users, and is really bad.
     #
     # Anyway - to enforce this, we actually don't give instances access to SVN.
     # If anything is missing from datastore, it'll be a 404. If the cronjobs
     # don't manage to catch everything - uhoh. On the other hand, we'll figure
     # it out pretty soon, and it also means that legitimate 404s are caught
     # before a round trip to SVN.
     if server_instance is None:
       # The ALWAYS_ONLINE thing is for tests and preview.py that shouldn't need
       # to run the cron before rendering things.
       constructor = (ServerInstance.CreateOnline if _ALWAYS_ONLINE else
                      ServerInstance.GetOrCreateOffline)
-      server_instance = constructor(channel)
+      server_instance = constructor(channel, base_path)
 
     canonical_path = server_instance.path_canonicalizer.Canonicalize(path)
     if path != canonical_path:
       return Response.Redirect(canonical_path if channel is None else
                                '%s/%s' % (channel, canonical_path))
 
     templates = server_instance.template_data_source_factory.Create(
         self._request, path)
 
     content = None
@@ skipping 28 matching lines @@
       return Response.NotFound(templates.Render('404'), headers=headers)
 
     if not content:
       logging.error('%s had empty content' % path)
 
     headers.update({
       'content-type': content_type,
       'cache-control': 'max-age=300',
     })
     return Response.Ok(content, headers=headers)