Put a copy of the wptrunner harness in-tree.

This is the same configuration as gecko and is convenient for making changes compared
to using releases from pypi

tests/wpt/harness/wptrunner/vcs.py

@@ -0,0 +1,53 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import subprocess
+from functools import partial
+
+from mozlog.structured import get_default_logger
+
+logger = None
+
+def vcs(bin_name):
+    def inner(command, *args, **kwargs):
+        global logger
+
+        if logger is None:
+            logger = get_default_logger("vcs")
+
+        repo = kwargs.pop("repo", None)
+        log_error = kwargs.pop("log_error", True)
+        if kwargs:
+            raise TypeError, kwargs
+
+        args = list(args)
+
+        proc_kwargs = {}
+        if repo is not None:
+            proc_kwargs["cwd"] = repo
+
+        command_line = [bin_name, command] + args
+        logger.debug(" ".join(command_line))
+        try:
+            return subprocess.check_output(command_line, stderr=subprocess.STDOUT, **proc_kwargs)
+        except subprocess.CalledProcessError as e:
+            if log_error:
+                logger.error(e.output)
+            raise
+    return inner
+
+git = vcs("git")
+hg = vcs("hg")
+
+
+def bind_to_repo(vcs_func, repo):
+    return partial(vcs_func, repo=repo)
+
+
+def is_git_root(path):
+    try:
+        rv = git("rev-parse", "--show-cdup", repo=path)
+    except subprocess.CalledProcessError:
+        return False
+    return rv == "\n"