Reland: Add omt-worker-fetch/external/wpt/referrer-policy

Reland of https://chromium-review.googlesource.com/1330903
with renaming due to crbug/906964.

Bug: 835717, 880027, 906964
Change-Id: I0eeca00cc7a0db2cb2efb16588b0cf52c14883f0
Reviewed-on: https://chromium-review.googlesource.com/c/1344434
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610983}

third_party/blink/web_tests/VirtualTestSuites

@@ -689,6 +689,11 @@
     "args": ["--enable-features=ServiceWorkerServicification",
              "--disable-features=NetworkService"]
   },
+  {
+    "prefix": "omt-worker-fetch",
+    "base": "external/wpt/referrer-policy",
+    "args": ["--enable-blink-features=OffMainThreadWorkerScriptFetch"]
+  },
   {
     "prefix": "omt-worker-fetch",
     "base": "external/wpt/workers",

third_party/blink/web_tests/virtual/omt-worker-fetch/external/wpt/referrer-policy/README.txt

+This directory is for testing off-the-main-thread top-level worker classic
+script loading. See https://crbug.com/835717.