build: use class path bases, not strings

scripts/slave/recipe_modules/webrtc/chromium_config.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.config import BadConf
 from recipe_engine.config_types import Path
 
 import DEPS
 CONFIG_CTX = DEPS['chromium'].CONFIG_CTX
 
 
 SUPPORTED_TARGET_ARCHS = ('intel', 'arm')
 
 
 @CONFIG_CTX(includes=['chromium', 'dcheck', 'webrtc_openh264'])
 def webrtc_standalone(c):
   _compiler_defaults(c)
 
-  c.runtests.memory_tests_runner = Path('[CHECKOUT]', 'tools',
-                                        'valgrind-webrtc', 'webrtc_tests',
-                                        platform_ext={'win': '.bat',
-                                                      'mac': '.sh',
-                                                      'linux': '.sh'})
+  c.runtests.memory_tests_runner = c.CHECKOUT_PATH.join(
+      'tools', 'valgrind-webrtc', 'webrtc_tests',
+      platform_ext={'win': '.bat', 'mac': '.sh', 'linux': '.sh'})
+
 @CONFIG_CTX(includes=['ninja', 'gcc', 'goma'])
 def webrtc_gcc(c):
   _compiler_defaults(c)
 
 @CONFIG_CTX(includes=['chromium_clang', 'dcheck', 'webrtc_openh264'])
 def webrtc_clang(c):
   _compiler_defaults(c)
 
 @CONFIG_CTX(includes=['gn'])
 def webrtc_gn(c):
@@ skipping 15 matching lines @@
 def webrtc_openh264(c):
   if c.TARGET_PLATFORM == 'ios':
     raise BadConf('ffmpeg decode not supported for iOS')  # pragma: no cover
   if c.TARGET_PLATFORM == 'android':
     raise BadConf('h264 decode not supported for Android')  # pragma: no cover
   c.gyp_env.GYP_DEFINES['ffmpeg_branding'] = 'Chrome'
   c.gyp_env.GYP_DEFINES['rtc_use_264'] = 1
 
 def _compiler_defaults(c):
   c.compile_py.default_targets = ['All']