Keep background thread alive even if alertserver down and add async request
Keep background thread alive even if alertserver down and add async request

This also gets rid of the js warning:
Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.

BUG=skia:5546

Review-Url: https://codereview.chromium.org/2184103002

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot