Use a pinned version of web-platform-tests/manifest.

third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/wpt/tools/manifest/utils.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/wpt/tools/manifest/utils.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/wpt/tools/manifest/utils.py b/third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/wpt/tools/manifest/utils.py
new file mode 100644
index 0000000000000000000000000000000000000000..d9be750e416935550e4442812b52531c709190bd
--- /dev/null
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/wpt/tools/manifest/utils.py
@@ -0,0 +1,51 @@
+import platform
+import os
+
+from six import BytesIO
+
+def rel_path_to_url(rel_path, url_base="/"):
+    assert not os.path.isabs(rel_path)
+    if url_base[0] != "/":
+        url_base = "/" + url_base
+    if url_base[-1] != "/":
+        url_base += "/"
+    return url_base + rel_path.replace(os.sep, "/")
+
+
+def from_os_path(path):
+    assert os.path.sep == "/" or platform.system() == "Windows"
+    rv = path.replace(os.path.sep, "/")
+    if "\\" in rv:
+        raise ValueError("path contains \\ when separator is %s" % os.path.sep)
+    return rv
+
+
+def to_os_path(path):
+    assert os.path.sep == "/" or platform.system() == "Windows"
+    if "\\" in path:
+        raise ValueError("normalised path contains \\")
+    return path.replace("/", os.path.sep)
+
+
+class ContextManagerBytesIO(BytesIO):
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args, **kwargs):
+        self.close()
+
+
+class cached_property(object):
+    def __init__(self, func):
+        self.func = func
+        self.__doc__ = getattr(func, "__doc__")
+        self.name = func.__name__
+
+    def __get__(self, obj, cls=None):
+        if obj is None:
+            return self
+
+        if self.name not in obj.__dict__:
+            obj.__dict__[self.name] = self.func(obj)
+            obj.__dict__.setdefault("__cached_properties__", set()).add(self.name)
+        return obj.__dict__[self.name]