chromium_tests: automatically set up test genrators

scripts/slave/recipe_modules/chromium_tests/chromium_recipe.md

 # Chromium Recipes: Reference Doc
 
 [TOC]
 
 ## I just want to....
 
 This section covers common tasks for chromium developers. If you want a more
 full background on the chromium recipes, go to the [Background](#Background)
 section.
 
@@ skipping 127 matching lines @@
 
     "Linux Builder": {
       "gtest_tests": [
         {
           "test": "base_unittests"
         },
       ...
       ]
     }
 
-Note that this relies on gtest generator in the bot configuration in the
-`chromium_tests` module. For example, given the file [`scripts/slave/recipe_modules/chromium_tests/chromium_linux.py`](https://code.google.com/p/chromium/codesearch#chromium/build/scripts/slave/recipe_modules/chromium_tests/chromium_linux.py)
-, you would need:
-
-    'Linux Builder': {
-      ...
-      'test_generators': [
-        steps.generate_gtest,
-        ...
-      ],
-      ...
-    },
-
 Changes to the JSON file can be tested on the trybots, and you can verify that
 they take effect and build still passes.
 
 ### Add a new non gtest-based test
 Generally, look at [steps.py](https://code.google.com/p/chromium/codesearch#chromium/build/scripts/slave/recipe_modules/chromium_tests/steps.py)
 , and either use an existing class there, or add a new one.
 
 ## Background
 Chromium tests are currently run on buildbot, and are organized by builders.
 A builder, in buildbot’s terminology, is a sequence of steps
@@ skipping 153 matching lines @@
 Path: [build/scripts/slave/recipe_modules/chromium_tests/api.py](https://code.google.com/p/chromium/codesearch#chromium/build/scripts/slave/recipe_modules/chromium/api.py)
 
 Implements methods like `configure_build`, `prepare_checkout`, compile, etc.
 that take configuration parameters and actually run the steps.
 
 ### src/testing/buildbot/*.json: per-master configs: targets & tests
 
 Example config: [src/testing/buildbot/chromium.mac.json](https://code.google.com/p/chromium/codesearch#chromium/src/testing/buildbot/chromium.mac.json&sq=package:chromium)
 
 These configs live in the project repo, and define additional compile targets and specific tests to run on each builder.