Tests: Use script type in isolate map. This makes trigger.py use the same code paths as the bots when they trigger standalone ANGLE tests. Fixes launching tests via trigger.py on Linux because of using the 'windowed_test_launcher' method that used xvfb. Bug: angleproject:5114 Change-Id: I073631270b5b69aac8f3f0f6378bd71f951ce8e6 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2464425 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>