recipe engine: extract infra-specific paths out of the engine

recipe_modules/raw_io/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 = [
   'path',
   'properties',
   'python',
   'raw_io',
   'step',
@@ skipping 31 matching lines @@
         api.raw_io.test_api.stream_output('blah\n') +
         api.raw_io.test_api.stream_output('fail\n', 'stderr')
       ))
   )
   assert step_result.stdout == 'blah\n'
   assert step_result.stderr == 'fail\n'
 
   # leak_to coverage.
   step_result = api.step(
       'leak stdout', ['echo', 'leaking'],
-      stdout=api.raw_io.output(leak_to=api.path['slave_build'].join('out.txt')),
+      stdout=api.raw_io.output(leak_to=api.path['tmp'].join('out.txt')),
       step_test_data=(
         lambda: api.raw_io.test_api.stream_output('leaking\n')))
   assert step_result.stdout == 'leaking\n'
 
   api.step('list temp dir', ['ls', api.raw_io.output_dir()])
   api.step('leak dir', ['ls', api.raw_io.output_dir(
-      leak_to=api.path['slave_build'].join('out'))])
+      leak_to=api.path['tmp'].join('out'))])
 
   # Example of overriding default mocked output for a single named output.
   step_result = api.python.inline(
       'override_default_mock',
       """
       import sys
       with open(sys.argv[1], 'w') as f:
         f.write(%r)
       """ % api.properties.get('some_prop', 'good_value'),
       args=[api.raw_io.output(name='test')],
@@ skipping 15 matching lines @@
   yield (api.test('basic') +
       api.properties(some_prop='bad_value') +
       api.step_data('echo',
           stdout=api.raw_io.output('Hello World\n'),
           stderr=api.raw_io.output('')) +
       api.step_data('cat',
           stdout=api.raw_io.output('hello')) +
       api.step_data('override_default_mock',
           api.raw_io.output('good_value', name='test'))
   )