Remove try-catch blocks from entry points. BUG=angle:700 Change-Id: I036901c397053a75677923304d7e1ed697c82aa2 Reviewed-on: https://chromium-review.googlesource.com/209570 Reviewed-by: <ehsan@mozilla.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>