tryserver recipe_module: Add get_tags.

recipe_modules/tryserver/example.py

 # Copyright 2014 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.
 
 DEPS = [
+  'recipe_engine/raw_io',
   'recipe_engine/path',
   'recipe_engine/platform',
   'recipe_engine/properties',
   'recipe_engine/python',
+  'recipe_engine/step',
   'tryserver',
 ]
 
 
 def RunSteps(api):
+  if api.properties.get('patch_text'):
+    api.step('patch_text test', [
+        'echo', str(api.tryserver.get_tags(api.properties['patch_text']))])
+    return
+
   api.path['checkout'] = api.path['slave_build']
   api.tryserver.maybe_apply_issue()
+  api.tryserver.get_tags()
   api.tryserver.get_files_affected_by_patch()
 
   if api.tryserver.is_tryserver:
     api.tryserver.set_subproject_tag('v8')
 
   api.tryserver.set_patch_failure_tryjob_result()
   api.tryserver.set_compile_failure_tryjob_result()
   api.tryserver.set_test_failure_tryjob_result()
   api.tryserver.set_invalid_test_results_tryjob_result()
 
   with api.tryserver.set_failure_hash():
     api.python.failing_step('fail', 'foo')
 
 
 def GenTests(api):
+  description_step = api.override_step_data(
+      'Get description', api.raw_io.output("foobar"))
   yield (api.test('with_svn_patch') +
-         api.properties(patch_url='svn://checkout.url'))
+         api.properties(patch_url='svn://checkout.url') +
+         description_step)
 
   yield (api.test('with_git_patch') +
          api.properties(
               patch_storage='git',
               patch_project='v8',
               patch_repo_url='http://patch.url/',
-              patch_ref='johndoe#123.diff'))
+              patch_ref='johndoe#123.diff') +
+         description_step)
 
   yield (api.test('with_rietveld_patch') +
-         api.properties.tryserver())
+         api.properties.tryserver() +
+         description_step)
 
-  yield (api.test('with_wrong_patch') + api.platform('win', 32))
+  yield (api.test('with_wrong_patch') + api.platform('win', 32) +
+         description_step)
+
+  yield (api.test('basic_tags') +
+         api.properties(
+             patch_text="hihihi\nfoo=bar")
+         )