depot_tools: add infra_paths recipe module for infra-specific paths (attempt #2)

recipe_modules/infra_paths/example.py

+# Copyright 2016 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 = [
+  'infra_paths',
+  'recipe_engine/path',
+  'recipe_engine/platform',
+  'recipe_engine/properties',
+  'recipe_engine/step',
+]
+
+
+def RunSteps(api):
+  api.step('show cache path', [])
+  api.step.active_result.presentation.step_text = str(api.path['cache'])
+
+
+def GenTests(api):
+  yield api.test('basic')
+
+  for platform in ('linux', 'mac', 'win'):
+    for path_config in ('buildbot', 'kitchen'):
+      yield (
+          api.test('paths_%s_%s' % (path_config, platform)) +
+          api.platform.name(platform) +
+          api.properties(path_config=path_config)
+      )