JS exceptions are being muted by exception reporting pipeline in production because of CORS-related settings. I'm not yet certain what and how, and this potentially could be attributed to preload-specific behavior. Also, fall back for such exceptions to default 'Script Error' message. @see https://bugs.chromium.org/p/gerrit/issues/detail?id=5471#c7 Change-Id: I073118002ef2516ae6c3d9ec02f0393e36caeaf3