[DevTools] Remove debug path from devtools test runner bindings

The current behavior of the web bindings is to load files from the debug
subdirectory of resources/inspector when the debug-devtools flag is set.
However, this does not work as the debug build does not include the
module information. Additionally, it is not necessary as the version of
the DevTools frontend in resources/inspector works just fine for the
debug case.

This CL, therefore, removes the redirection from resources/inspector to
resources/inspector/debug, and in the process allows DevTools developers
to run `npm run debug-test` from the DevTools repo successfully.

R=tvanderlippe@chromium.org

Change-Id: I036697bd99cbc6c010a6be3bd17511fce7ee28d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2489628
Auto-Submit: Paul Lewis <aerotwist@chromium.org>
Reviewed-by: Tim van der Lippe <tvanderlippe@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Mike West <mkwst@chromium.org>
Commit-Queue: Paul Lewis <aerotwist@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819767}

content/web_test/browser/web_test_devtools_bindings.cc

@@ -79,8 +79,6 @@ GURL WebTestDevToolsBindings::MapTestURLIfNeeded(const GURL& test_url,
       switches::kDebugDevTools);
   // The test runner hosts DevTools resources at this path.
   std::string url_string = "http://localhost:8000/inspector-sources/";
-  if (is_debug_dev_tools)
-    url_string += "debug/";
   url_string += "integration_test_runner.html?experiments=true";
   if (is_debug_dev_tools)
     url_string += "&debugFrontend=true";