Use src-side launcher for telemetry_unittests in chromium_trybot recipe

scripts/slave/recipe_modules/chromium/api.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.
 
 import os
 import re
 
 from slave import recipe_api
 from slave import recipe_util
 
@@ skipping 605 matching lines @@
     # Chromium workspace.
     if self.m.platform.is_win:
       self.m.python(
           name='get_vs_toolchain_if_necessary',
           script=self.m.path['depot_tools'].join(
               'win_toolchain', 'get_toolchain_if_necessary.py'),
           args=[
               '27eac9b2869ef6c89391f305a3f01285ea317867',
               '9d9a93134b3eabd003b85b4e7dea06c0eae150ed',
           ])
+
+  def get_common_args_for_scripts(self):
+    args = []
+
+    args.extend(['--build-config-fs', self.c.build_config_fs])
+
+    paths = {}
+    for path in ('build',):
+      paths[path] = self.m.path[path]
+    args.extend(['--paths', self.m.json.input(paths)])
+
+    properties = {}
+    for name in ('buildername', 'slavename', 'buildnumber'):

[iannucci, 2014/10/21 18:02:47]

yikes! buildnumber is /extremely dangerous/. What is using it?

[Paweł Hajdan Jr., 2014/10/22 11:18:26]

e.g. runtest.py

Could you explain more though why it's dangerous?

By the way I added a TODO to remove this. Note that I believe this is not any
worse than the current state of things where we use buildnumber anyway with
runtest.py. Here we at least have a much shorter list of build properties.

[iannucci, 2014/10/22 18:58:41]

It's ephemeral data. It's not tied to anything real, and only exists in the
buildbot database:
  * if you remove and re-add a builder, it resets
  * if you rename the builder, it resets
  * if the master crashes (sometimes we need to wipe old data when that
happens), it can reset
  * if we split the master, it resets
  * if we merge the masters, it resets
  * if the db corrupts (no backups :), it resets
  * if you build out-of-order with the source (e.g. force build), and you use it
to indicate a timeline of source, you'll have out-of-order data points!
  * it is tied to buildbot... there's no way to reproduce a
buildnumber-like-number without a centralized master like buildbot. if we start
getting rid of it now, it'll make our post-buildbot transition that much easier
:)

It's basically not trustworthy for what people expect it to be. A much better
thing to use would be the real revision, or some numerical representation of
that (probably the commit position number).
Yes, you're correct, it's better than right now :)

+      properties[name] = self.m.properties[name]
+    args.extend(['--properties', self.m.json.input(properties)])
+
+    return args
+
+  def get_compile_targets_for_scripts(self):
+    return self.m.python(
+        name='get compile targets for scripts',
+        script=self.m.path['checkout'].join(
+            'testing', 'scripts', 'get_compile_targets.py'),
+        args=[
+            '--output', self.m.json.output(),
+            '--',
+        ] + self.get_common_args_for_scripts(),
+        step_test_data=lambda: self.m.json.test_api.output({}))