Fix failure to write latest_rev updates to database.

app.py

 # Copyright (c) 2012 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 __future__ import with_statement
 
 import datetime
 import json
 import logging
 import os
@@ skipping 250 matching lines @@
   if not prev_rev or rev_number > prev_rev['rev_number']:
     latest_rev_row = {
         'rev_number': rev_number,
         'fetch_timestamp': datetime.datetime.now(),
         'rev': None,
         'name': None,
         'status': None,
         'comment': None,
         'details': None,
     }
-    save_row(latest_rev_row, 'latest_rev')
+    prev_rev_db = get_or_create_row('latest_rev', rev_number)
+    prev_rev_db.fetch_timestamp = datetime.datetime.now()
+    prev_rev_db.rev_number = rev_number
+    prev_rev_db.put()
+    put_data_into_cache('latest_rev', latest_rev_row)
 
 
 ##########
 # ConsoleData class definition and related functions.
 ##########
 class ConsoleData(object):
   def __init__(self):
     self.row_orderedkeys = []
     self.row_data = {}
 
@@ skipping 908 matching lines @@
   # LKGR JSON.
   {
     'remoteurl':
         ('http://build.chromium.org/p/chromium.lkgr/json/builders/Linux%20x64/'
          'builds/-1?as_text=1'),
     'localpath':
         'chromium.lkgr/json/builders/Linux%20x64/builds/-1/as_text=1.json',
     'maxage': 2*60,  # 2 mins
   },
 ]