[Findit] Add iterator and crash_iterator for delta test

appengine/findit/util_scripts/crash_queries/crash_printer/crash_printer.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.
+
+from crash_queries import crash_iterator
+
+CRASH_INFO_FIELDS = ['signature', 'platform']
+
+
+def PrintCrashInfo(crash):
+  print '\nCrash %s' % crash['id']
+  for crash_info_field in CRASH_INFO_FIELDS:
+    print '%s: %s' % (crash_info_field, crash[crash_info_field])
+
+
+def CrashPrinter(client_id,
+                 start_date, end_date,
+                 print_func=PrintCrashInfo,
+                 app_id=None):
+  for crash in crash_iterator.IterateCrashes(client_id,
+                                             fields=CRASH_INFO_FIELDS,
+                                             start_date=start_date,
+                                             end_date=end_date,
+                                             app_id=app_id):
+    print_func(crash)