Fix double serving of files in component server
Fix double serving of files in component server

Now the server can serve from the tests directory, it will sometimes get
two requests for the same file, one prefixed with front_end and the
other not. If that happens the server now redirects the request such
that we only ever serve each file once and the browser doesn't
double-execute a module.

Change-Id: I14b44aad8b16d1c3f2f787082c70532a8f8776e9
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2599746
Auto-Submit: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@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