[Android] Add context manager to record logcat during step(s).

scripts/slave/recipes/android_webview_cts_tests.py

 # Copyright 2015 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.
 
 """
 Recipe for running WebView CTS using system WebView.
 """
 DEPS = [
   'adb',
   'bot_update',
@@ skipping 99 matching lines @@
   for failed_class in failed_classes:
     failed_class_name = 'android.webkit.cts.' + failed_class.get('name')
     if failed_class_name not in EXPECTED_FAILURE:
       api.step.active_result.presentation.status = api.step.FAILURE
       continue
     failed_methods = failed_class.findall('Test/FailedScene/..')
     for failed_method in failed_methods:
       if failed_method.get('name') not in EXPECTED_FAILURE[failed_class_name]:
         api.step.active_result.presentation.status = api.step.FAILURE
 
-  api.chromium_android.logcat_dump()
-  api.chromium_android.stack_tool_steps()
+  logcat_file = api.chromium.output_dir.join('full_logcat')
+  api.chromium_android.logcat_dump(output_logcat_file=logcat_file)
+  api.chromium_android.stack_tool_steps(logcat_file=logcat_file)
   api.chromium_android.test_report()
 
 def GenTests(api):
   result_xml_with_unexecuted_tests = """<TestResult>
                           <TestPackage>
                             <TestSuite name='android'>
                               <TestSuite name='webkit'>
                                 <TestSuite name='cts'>
                                   <TestCase name='WebSettingsTest'>
                                     <Test name='test' result='notExecuted'>
@@ skipping 83 matching lines @@
       api.override_step_data('Read test result and report failures',
           api.raw_io.output(result_xml_with_unexpected_failure_method)) + \
       api.properties.generic(mastername='chromium.android')
 
   yield api.test('Test_parsing_invalid_cts_output') + \
       api.override_step_data('Run Cts', api.raw_io.stream_output(
           'Invalid CTS output here...',
           stream='stdout')) + \
       api.properties.generic(mastername='chromium.android') + \
       api.expect_exception('Exception')