Extensions: Fix DocServer assert failures.

chrome/common/extensions/docs/server2/availability_finder.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 posixpath
 
 from api_models import GetNodeCategories
 from api_schema_graph import APISchemaGraph
 from branch_utility import BranchUtility, ChannelInfo
 from compiled_file_system import Cache, CompiledFileSystem, SingleFile, Unicode
@@ skipping 126 matching lines @@
     self._schema_processor = schema_processor_factory.Create(True)
 
   def _GetPredeterminedNodeAvailability(self, node_name):
     '''Checks a configuration file for hardcoded (i.e. predetermined)
     availability information for an API node.
     '''
     node_info = self._json_fs.GetFromFile(
         JSON_TEMPLATES + 'api_availabilities.json').Get().get(node_name)
     if node_info is None:
       return None
+
+    channel_info = None
     if node_info['channel'] == 'stable':
-      return AvailabilityInfo(
-          self._branch_utility.GetStableChannelInfo(node_info['version']))
-    return AvailabilityInfo(
-        self._branch_utility.GetChannelInfo(node_info['channel']))
+      channel_info = self._branch_utility.GetStableChannelInfo(
+          node_info['version'])
+    else:
+      channel_info = self._branch_utility.GetChannelInfo(node_info['channel'])
+    return AvailabilityInfo(channel_info) if channel_info else None
 
   @memoize
   def _CreateAPISchemaFileSystem(self, file_system):
     '''Creates a CompiledFileSystem for parsing raw JSON or IDL API schema
     data and formatting it so that it can be used to create APISchemaGraphs.
     '''
     def process_schema(path, data):
       return self._schema_processor.Process(path, data)
     return self._compiled_fs_factory.Create(
         file_system,
@@ skipping 293 matching lines @@
       # Continue looping until there are no longer differences between this
       # version and master.
       return version_stat != master_stat
 
     self._file_system_iterator.Ascending(
         self.GetAPIAvailability(api_name).channel_info,
         update_availability_graph)
 
     self._node_level_object_store.Set(api_name, availability_graph)
     return availability_graph