The error thrower did allocate the exception at the moment the error was
detected. For async compilation, this meant in another step than when
it was actually thrown. Since the HandleScope of the exception already
died at that point, this would have lead to memory errors.

With this refactoring, we only store the information needed to generate
the exception in the ErrorThrower, and only generate the exception
object once it is actually needed.

With regression test.

R=ahaas@chromium.org, mtrofin@chromium.org
Also-by: ahaas@chromium.org

Change-Id: Iffcab1f8d1cf5925e3643fcf0729ba9a84c7d277
Reviewed-on: https://chromium-review.googlesource.com/490085
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45000}