We assumed that if the ErrorThrower is empty after instantiation, then
instantiation succeeded and an instance exists which we can return.
However, if the start function throws, no instance exists, which caused
a crash. With this CL we handle execeptions thrown by the start
function correctly.


R=clemensh@chromium.org

Bug: chromium:848966
Change-Id: I51dc94e6bc563aa4a4b88c44a14e831af913fbd8
Reviewed-on: https://chromium-review.googlesource.com/1092234Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53687}