Refactor the way that TestApi works so that it is actually useful.

scripts/slave/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.
 
 DEPS = [
   'step',
 ]
 
 
 def GenSteps(api):
   # We are going to have steps with the same name, so fix it automagically.
   api.step.auto_resolve_conflicts = True
 
   # The api.step object is directly callable.
   yield api.step('hello', ['echo', 'Hello World'])
   yield api.step('hello', ['echo', 'Why hello, there.'])
 
   # You can also manipulate various aspects of the step, such as env.
   # These are passed straight through to subprocess.Popen.
   # Also, abusing bash -c in this way is a TERRIBLE IDEA DON'T DO IT.
   yield api.step('goodbye', ['bash', '-c', 'echo Good bye, $friend.'],
                  env={'friend': 'Darth Vader'})
 
 
-def GenTests(_api):
-  yield 'basic', {}
+def GenTests(api):
+  yield api.Test('basic')