Typecheck changes/ChangesHighlighter.js with TypeScript
Typecheck changes/ChangesHighlighter.js with TypeScript

Unfortunately the typings in `@types/CodeMirror` are most of the
time incorrect and require several upstream patches to make them
pass. For now, we are ignoring these issues, to unblock numerous
other build infrastructure changes we need to make.

R=8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org

Bug: 1011811
Change-Id: I730663b0dc6ef9ff85d5d4a2cc58403a39d7d921
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2534203
Auto-Submit: Tim van der Lippe <dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org>
Commit-Queue: Paul Lewis <8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org>
Reviewed-by: Paul Lewis <8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org>

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend