recipe_engine: change resource API to use repo root

recipe_modules/step/example.py

 # Copyright 2013 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.
 
 from recipe_engine import recipe_api, config
 
 DEPS = [
   'path',
   'properties',
   'step',
@@ skipping 26 matching lines @@
   # Also, abusing bash -c in this way is a TERRIBLE IDEA DON'T DO IT.
   api.step('goodbye', ['bash', '-c', 'echo Good bye, $friend.'],
            env={'friend': 'Darth Vader'})
 
   # You can modify environment in terms of old environment. Environment
   # variables are substituted in for expressions of the form %(VARNAME)s.
   api.step('recipes help',
       ['recipes.py', '--help'],
       env={
         'PATH': api.path.pathsep.join(
-            [str(api.step.package_resource()), '%(PATH)s']),
+            [str(api.step.package_repo_resource()), '%(PATH)s']),
       })
 
   # Finally, you can make your step accept any return code
   api.step('anything is cool', ['bash', '-c', 'exit 3'],
            ok_ret='any')
 
   # We can manipulate the step presentation arbitrarily until we run
   # the next step.
   step_result = api.step('hello', ['echo', 'hello'])
   step_result.presentation.status = api.step.EXCEPTION
@@ skipping 91 matching lines @@
       api.test('infra_failure') +
       api.properties(raise_infra_failure=True) +
       api.step_data('cleanup', retcode=1)
     )
 
   yield (
       api.test('bad_return') +
       api.properties(bad_return=True) +
       api.expect_exception('TypeError')
     )