Fix bot_update api rename.

scripts/slave/recipes/flutter/engine.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 contextlib
 
 DEPS = [
   'depot_tools/bot_update',
   'depot_tools/gclient',
   'file',
   'gsutil',
   'recipe_engine/path',
   'recipe_engine/platform',
   'recipe_engine/properties',
   'recipe_engine/step',
   'zip',
 ]
 
 BUCKET_NAME = 'flutter_infra'
 
 def GetCloudPath(api, path):
-  # TODO(eseidel): api.bot_update.properties is supposedly a known api wart.
-  # iannucci says it will be improved at some point.
-  git_hash = api.bot_update.properties['got_engine_revision']
+  # TODO(eseidel): api.bot_update.last_returned_properties is supposedly a known
+  # api wart. iannucci says it will be improved at some point.
+  git_hash = api.bot_update.last_returned_properties['got_engine_revision']
   return 'flutter/%s/%s' % (git_hash, path)
 
 
 def Build(api, config, *targets):
   checkout = api.path['checkout']
   build_dir = checkout.join('out/%s' % config)
   ninja_args = ['ninja', '-C', build_dir]
   ninja_args.extend(targets)
   api.step('build %s' % ' '.join([config] + list(targets)), ninja_args)
 
@@ skipping 208 matching lines @@
       GenerateXcodeProject(api)
 
 
 def GenTests(api):
   # A valid commit to flutter/engine, to make the gsutil urls look real.
   for platform in ('mac', 'linux'):
     yield (api.test(platform) + api.platform(platform, 64)
         + api.properties(mastername='client.flutter',
               buildername='%s Engine' % platform.capitalize(),
               slavename='fake-m1', clobber=''))