Service Worker: Detect unhandled errors in 'install' or 'activate' event handlers

As per the spec, if any uncaught runtime script error occurs in these event
handlers, the installation/activation should not succeed.

BUG=425960

Review URL: https://codereview.chromium.org/684783007

git-svn-id: svn://svn.chromium.org/blink/trunk@184637 bbb929c8-8fbe-4397-9dbb-9b2b20218538