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

scripts/slave/recipes/android_webview_shell_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 SystemWebViewShell instrumentation layout tests using
 system WebView.
 """
 
 from recipe_engine.types import freeze
@@ skipping 68 matching lines @@
   api.chromium_android.adb_install_apk(WEBVIEW_APK)
 
   # Install system WebView shell
   api.chromium_android.adb_install_apk(WEBVIEW_SHELL_APK)
 
   api.adb.list_devices()
 
   # Run the instrumentation tests from the package.
   run_tests(api)
 
-  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 run_tests(api):
   droid = api.chromium_android
   mock_test_results = {
     'per_iteration_data': [{'TestA': [{'status': 'SUCCESS'}]},
                            {'TestB': [{'status': 'FAILURE'}]}]
   }
   for suite in INSTRUMENTATION_TESTS:
     json_results_file = api.json.output(add_json_log=False)
@@ skipping 12 matching lines @@
           [test_name for test_name, test_status in test_results.iteritems()
            if test_status not in ['SUCCESS', 'SKIPPED']])
     except Exception:  # pragma: no cover
       failures = []
     step_result.presentation.step_text += api.test_utils.format_step_text(
         [['failures:', failures]])
 
 
 def GenTests(api):
   yield api.test('basic') + api.properties.scheduled()