Stop to use contextmanager for goma.build_with_goma

scripts/slave/recipe_modules/goma/example.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 re
 
 DEPS = [
   'goma',
   'recipe_engine/platform',
   'recipe_engine/properties',
   'recipe_engine/step',
 ]
 
 def RunSteps(api):
   api.goma.ensure_goma()
   api.step('gn', ['gn', 'gen', 'out/Release',
                   '--args=use_goma=true goma_dir=%s' % api.goma.goma_dir])
 
   command = list(api.properties.get('build_command'))
   env = {}
   allow_build_without_goma = api.properties.get(
       'allow_build_without_goma', False)
 
   with api.goma.build_with_goma(
       ninja_log_outdir=api.properties.get('ninja_log_outdir'),
       ninja_log_compiler=api.properties.get('ninja_log_compiler'),
       ninja_log_command=command,
       allow_build_without_goma=allow_build_without_goma,
-      env=env):
-    if 'GOMA_DISABLED' in env:
-      api.goma.remove_j_flag(command)
-      api.step('ninja', command, env=env)
-    else:
-      # build something using goma.
-      api.step('echo goma jobs',
-               ['echo', str(api.goma.recommended_goma_jobs)])
-      api.step('echo goma jobs second',
-               ['echo', str(api.goma.recommended_goma_jobs)])
-      api.step('ninja', command, env=env)
+      env=env) as (env_update, ninja_command):
+    env.update(env_update)
+    # build something using goma.
+    api.step('echo goma jobs',
+             ['echo', str(api.goma.recommended_goma_jobs)])
+    api.step('echo goma jobs second',
+             ['echo', str(api.goma.recommended_goma_jobs)])
+    api.step('ninja', ninja_command, env=env)
 
 def GenTests(api):
   for platform in ('linux', 'win', 'mac'):
     properties = {
         'buildername': 'test_builder',
         'mastername': 'test_master',
         'slavename': 'test_slave',
         'clobber': '1',
         'build_command': ['ninja', '-C', 'out/Release', '-j', '500'],
         'ninja_log_outdir': 'out/Release',
         'ninja_log_compiler': 'goma',
         'build_data_dir': 'build_data_dir',
     }
 
     yield (api.test(platform) + api.platform.name(platform) +
            api.properties.generic(**properties))
 
     yield (api.test('%s_goma_disabled' % platform) +
            api.step_data('preprocess_for_goma.start_goma', retcode=1) +
            api.platform.name(platform) +
            api.properties(allow_build_without_goma=True) +
            api.properties.generic(**properties))