[Findit] Add cracas_crash_analysis

appengine/findit/model/crash/crash_analysis.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 hashlib
 import json
 import logging
 
 from google.appengine.ext import ndb
 
 from model import analysis_status
 from model import triage_status
 
 
 class CrashAnalysis(ndb.Model):
@@ skipping 112 matching lines @@
   @property
   def failed(self):
     return self.status == analysis_status.ERROR
 
   @property
   def duration(self):
     if not self.completed:
       return None
 
     return int((self.completed_time - self.started_time).total_seconds())
+
+  @classmethod
+  def _CreateKey(cls, crash_identifiers):
+    return ndb.Key(cls.__name__, hashlib.sha1(
+        json.dumps(crash_identifiers, sort_keys=True)).hexdigest())
+
+  @classmethod
+  def Get(cls, crash_identifiers):
+    return cls._CreateKey(crash_identifiers).get()
+
+  @classmethod
+  def Create(cls, crash_identifiers):
+    return cls(key=cls._CreateKey(crash_identifiers))