Revert "Headless: don't use the copy of the protocol test harness, re…

…ference the original."

This reverts commit fec1b5f.

Reason for revert: headless bots failing

Original change's description:
> Headless: don't use the copy of the protocol test harness, reference the original.
> 
> Change-Id: If7796d2a698243b89a9ee7ff9603cf3e04338be3
> TBR: eseckler
> Reviewed-on: https://chromium-review.googlesource.com/1066683
> Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#560103}

TBR=dgozman@chromium.org,pfeldman@chromium.org,johannes@chromium.org

Change-Id: I962809483fd18c2635cb4f963b215b69b47c5efe
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/1066746
Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Commit-Queue: Pavel Feldman <pfeldman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#560154}

headless/BUILD.gn

@@ -772,7 +772,6 @@ test("headless_browsertests") {
     "lib/dom_tree_extraction_expected_styles.txt",
     "$root_out_dir/headless_lib.pak",
     "//net/tools/testserver/",
-    "//third_party/WebKit/LayoutTests/http/tests/inspector-protocol/",
     "//third_party/pyftpdlib/",
     "//third_party/pywebsocket/",
     "//third_party/tlslite/",

headless/test/data/protocol/inspector-protocol-test.html

@@ -20,7 +20,7 @@
   console.debug(object.params[0]);
 }
 </script>
-<script src="../../resources/inspector-protocol-test.js"></script>
+<script src="inspector-protocol-test.js"></script>
 <script>
 DevToolsAPI._log = (text) => output.push(text);
 function onmessage(json) { DevToolsAPI.dispatchMessage(json); }