[Predator] Add CrashData class to process raw json crash data.

appengine/findit/crash/changelist_classifier.py

 # Copyright 2016 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 logging
 from collections import defaultdict
 from collections import namedtuple
 
 from common.chrome_dependency_fetcher import ChromeDependencyFetcher
 from crash import crash_util
@@ skipping 181 matching lines @@
                 }),
             ]
         }
     }
 
     reverted_cls (set): A set of reverted revisions.
   """
   dep_to_file_to_changelogs = defaultdict(lambda: defaultdict(list))
   reverted_cls = set()
 
-  for dep in stack_deps:
+  for dep in stack_deps or []:

[Martin Barbella, 2017/02/06 21:16:12]

At a glance it seems like it'd be cleaner to ensure that stack_deps is iterable
wherever we create it. In the event that we start using it in other places
later, we'd have to add these same kinds of checks.

[Sharu Jiang, 2017/02/10 22:07:20]

Done.

     # If a dep is not in regression range, than it cannot be the dep of
     # culprits.
     dep_roll = regression_deps_rolls.get(dep)
     if not dep_roll:
       continue
 
     repository = get_repository(dep_roll.repo_url)
     changelogs = repository.GetChangeLogs(dep_roll.old_revision,
                                           dep_roll.new_revision)
 
@@ skipping 92 matching lines @@
         repository = get_repository(stack_deps[dep].repo_url)
         blame = repository.GetBlame(touched_file_path,
                                     stack_deps[dep].revision)
 
         # Generate/update each suspect(changelog) in changelogs, blame is used
         # to calculate distance between touched lines and crashed lines in file.
         suspects.GenerateSuspects(
             touched_file_path, dep, stack_infos, changelogs, blame)
 
   return suspects.values()