[Findit] Add a sub-pipeline to analyze failures caused by DEPS rolls.

appengine/findit/waterfall/detect_first_failure_pipeline.py

 # Copyright 2014 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 collections
 from datetime import datetime
 import logging
 import random
 import time
 
@@ skipping 35 matching lines @@
       # Retrieve build data from build archive first.
       build.data = buildbot.GetBuildDataFromArchive(
           build.master_name, build.builder_name, build.build_number,
           self.HTTP_CLIENT)
 
       if build.data is None:
         if not lock_util.WaitUntilDownloadAllowed(
             master_name):  # pragma: no cover
           raise pipeline.Retry('Too many download from %s' % master_name)
 
-        # Retrieve build data from build master. 
+        # Retrieve build data from build master.
         build.data = buildbot.GetBuildDataFromBuildMaster(
             build.master_name, build.builder_name, build.build_number,
             self.HTTP_CLIENT)
 
       build.last_crawled_time = datetime.utcnow()
       build.put()
 
     return build
 
   def _ExtractBuildInfo(self, master_name, builder_name, build_number):
@@ skipping 162 matching lines @@
     build_info = self._ExtractBuildInfo(master_name, builder_name, build_number)
 
     if not build_info:  # pragma: no cover
       raise pipeline.Retry('Failed to extract build info.')
 
     failure_info = {
         'failed': True,
         'master_name': master_name,
         'builder_name': builder_name,
         'build_number': build_number,
+        'chromium_revision': build_info.chromium_revision,
         'builds': {},
         'failed_steps': [],
     }
 
     if (build_info.result == buildbot.SUCCESS or
         not build_info.failed_steps):
       failure_info['failed'] = False
       return failure_info
 
     builds = dict()
     self._SaveBlamelistAndChromiumRevisionIntoDict(build_info, builds)
 
     failed_steps = self._CreateADictOfFailedSteps(build_info)
 
     self._CheckForFirstKnownFailure(
         master_name, builder_name, build_number, failed_steps, builds)
 
     failure_info['builds'] = builds
     failure_info['failed_steps'] = failed_steps
     return failure_info