Reland "Add script that checks license headers of JavaScript files"

This reverts commit 27f15d113aa302bb3f93421ab1ff62f1734b9c36.

Reason for revert: script is fixed on Windows

Original change's description:
> Revert "Add script that checks license headers of JavaScript files"
>
> This reverts commit 6122ebd2f94da85ec430709dea158e2395610a55.
>
> Reason for revert: Presubmit fails on windows due to relative
> path comparison with excluded files
>
> Original change's description:
> > Add script that checks license headers of JavaScript files
> >
> > The script checks if the license header is the BSD-3 license header that
> > DevTools is licensed under. It excludes files that have license headers
> > that reference non-Google/non-Chromium authors or are third_party
> > bundles that are checked into a non-third_party folder.
> >
> > Change-Id: I35f78036b48d3d7b7dcb9db1e070691282e27a02
> > Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2016747
> > Commit-Queue: Tim van der Lippe <tvanderlippe@chromium.org>
> > Reviewed-by: Liviu Rau <liviurau@chromium.org>
> > Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
>
> TBR=bmeurer@chromium.org,aerotwist@chromium.org,tvanderlippe@chromium.org,liviurau@chromium.org
>
> Change-Id: Idc27e9b78d5ac314176c71f8f4a7a2257da08be9
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2019019
> Reviewed-by: Lorne Mitchell <lomitch@microsoft.com>
> Reviewed-by: Brandon Goddard <brgoddar@microsoft.com>
> Commit-Queue: Brandon Goddard <brgoddar@microsoft.com>

TBR=bmeurer@chromium.org,aerotwist@chromium.org,lomitch@microsoft.com,brgoddar@microsoft.com,tvanderlippe@chromium.org,liviurau@chromium.org

Change-Id: I191665c8e3fdbee7f3c5c312b5ba00513502e080
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2019021
Reviewed-by: Fabio Rocha <fabio.rocha@microsoft.com>
Commit-Queue: Brandon Goddard <brgoddar@microsoft.com>
diff --git a/scripts/javascript_natives/index.js b/scripts/javascript_natives/index.js
index c00369c..2d37b54 100644
--- a/scripts/javascript_natives/index.js
+++ b/scripts/javascript_natives/index.js
@@ -190,7 +190,10 @@
 
   fs.writeFileSync(
       path.join(__dirname, '..', '..', 'front_end', 'javascript_metadata', 'NativeFunctions.js'),
-      `// Generated from ${path.relative(path.join(__dirname, '..', '..'), __filename)}
+      `// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+// Generated from ${path.relative(path.join(__dirname, '..', '..'), __filename)}
 export const NativeFunctions = ${JSON.stringify(functions)};
 `);
 }