Put a copy of the wpt upstreaming scripts in-tree.

This is copied from gecko, which is slightly unfortunate. However it allows
committing changes to wpt directly in-tree and having them upstreamed in the
next update.

tests/wpt/update/update.py

@@ -0,0 +1,42 @@
+# 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 os
+
+from wptrunner.update.base import Step, StepRunner
+from wptrunner.update.update import LoadConfig, SyncFromUpstream, UpdateMetadata
+from wptrunner.update.tree import NoVCSTree
+
+from .tree import GitTree, HgTree, GeckoCommit
+from .upstream import SyncToUpstream
+
+class LoadTrees(Step):
+    """Load gecko tree and sync tree containing web-platform-tests"""
+
+    provides = ["local_tree", "sync_tree"]
+
+    def create(self, state):
+        if os.path.exists(state.sync["path"]):
+            sync_tree = GitTree(root=state.sync["path"])
+        else:
+            sync_tree = None
+
+        if GitTree.is_type():
+            local_tree = GitTree(commit_cls=GeckoCommit)
+        elif HgTree.is_type():
+            local_tree = HgTree(commit_cls=GeckoCommit)
+        else:
+            local_tree = NoVCSTree()
+
+        state.update({"local_tree": local_tree,
+                      "sync_tree": sync_tree})
+
+
+class UpdateRunner(StepRunner):
+    """Overall runner for updating web-platform-tests in Gecko."""
+    steps = [LoadConfig,
+             LoadTrees,
+             SyncToUpstream,
+             SyncFromUpstream,
+             UpdateMetadata]