Revert r144460 "Remove the linux-only CR_SOURCE_ROOT environment variable override of base::DIR_SOU…

testing/test_env.py

Index: testing/test_env.py
diff --git a/testing/test_env.py b/testing/test_env.py
index 410f812edfb3e0061c2698b9eab73b0f269030d6..1d8bff87af3cea65dffe5e748d450f843edfe7e7 100755
--- a/testing/test_env.py
+++ b/testing/test_env.py
@@ -25,11 +25,15 @@ def fix_python_path(cmd):
 
 def run_executable(cmd, env):
   """Runs an executable with:
+    - environment variable CR_SOURCE_ROOT set to the root directory.
     - environment variable LANGUAGE to en_US.UTF-8.
     - Reuses sys.executable automatically.
   """
   # Many tests assume a English interface...
   env['LANGUAGE'] = 'en_US.UTF-8'
+  # Used by base/base_paths_linux.cc as an override. Just make sure the default
+  # logic is used.
+  env.pop('CR_SOURCE_ROOT', None)
   # Ensure paths are correctly separated on windows.
   cmd[0] = cmd[0].replace('/', os.path.sep)
   cmd = fix_python_path(cmd)