[Culprit-Finder] Seperate gae related part in cache_decorator and gitile repository to gae_libs/

appengine/findit/waterfall/pull_changelog_pipeline.py

 # Copyright 2015 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 common.http_client_appengine import HttpClientAppengine as HttpClient
 from common.pipeline_wrapper import BasePipeline
 from common.pipeline_wrapper import pipeline
-from lib.gitiles.gitiles_repository import GitilesRepository
+from gae_libs.gitiles.cached_gitiles_repository import CachedGitilesRepository
 
 
 class PullChangelogPipeline(BasePipeline):
   """A pipeline to pull change log of CLs."""
 
   # TODO: for files in dependencies(blink, v8, skia, etc), use blame first.
-  GIT_REPO = GitilesRepository(
+  GIT_REPO = CachedGitilesRepository(
       HttpClient(), 'https://chromium.googlesource.com/chromium/src.git')
 
   # Arguments number differs from overridden method - pylint: disable=W0221
   def run(self, failure_info):
     """
     Args:
       failure_info (dict): Output of pipeline DetectFirstFailurePipeline.run().
 
     Returns:
       A dict with the following form:
       {
         'git_hash_revision1': common.change_log.ChangeLog.ToDict(),
         ...
       }
     """
     change_logs = {}
     if not failure_info['failed'] or not failure_info['chromium_revision']:
       # Bail out if no failed step or no chromium revision.
       return change_logs
 
     for build in failure_info.get('builds', {}).values():
       for revision in build['blame_list']:
         change_log = self.GIT_REPO.GetChangeLog(revision)
         if not change_log:  # pragma: no cover
           raise pipeline.Retry('Failed to get change log for %s' % revision)
 
         change_logs[revision] = change_log.ToDict()
 
     return change_logs