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

third_party/WebKit/Tools/Scripts/webkitpy/w3c/deps_updater_unittest.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/w3c/deps_updater_unittest.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/w3c/deps_updater_unittest.py b/third_party/WebKit/Tools/Scripts/webkitpy/w3c/deps_updater_unittest.py
index 46427f553359c5846fa0ee3d98bae3b1ad96acb4..221c58fc89a54998d51182f8efad791fe5a776f9 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/w3c/deps_updater_unittest.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/w3c/deps_updater_unittest.py
@@ -104,9 +104,6 @@ class DepsUpdaterTest(unittest.TestCase):
         # This test doesn't test any aspect of the real manifest script, it just
         # asserts that DepsUpdater._generate_manifest would invoke the script.
         host = MockHost()
-        host.filesystem.files = {
-            '/mock-checkout/third_party/WebKit/wpt/manifest': 'dummy content'
-        }
         updater = DepsUpdater(host)
         updater._generate_manifest(
             '/mock-checkout/third_party/WebKit/wpt',
@@ -115,7 +112,7 @@ class DepsUpdaterTest(unittest.TestCase):
             host.executive.calls,
             [
                 [
-                    '/mock-checkout/third_party/WebKit/wpt/manifest',
+                    '/mock-checkout/third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/manifest',
                     '--work',
                     '--tests-root',
                     '/mock-checkout/third_party/WebKit/LayoutTests/imported/wpt'