Update Mocha to 8.0.1

Breaking changes here https://github.com/mochajs/mocha/releases/tag/v8.0.0
seem fine.

DISABLE_THIRD_PARTY_CHECK=Update Mocha

Bug: chromium:1101784
Change-Id: Idc75c94f9a923e2b0ca13d1d1331540cb1c5d3a3
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2279830
Reviewed-by: Tim van der Lippe <tvanderlippe@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
diff --git a/node_modules/diff/runtime.js b/node_modules/diff/runtime.js
new file mode 100644
index 0000000..82ea7e6
--- /dev/null
+++ b/node_modules/diff/runtime.js
@@ -0,0 +1,3 @@
+require('@babel/register')({
+  ignore: ['lib', 'node_modules']
+});