At the moment the AsyncCompileJob object is deallocated after one of its
task functions return false. This mechanism is, however, not documented,
potentially error-prone, and I think there are already some cases where
I think that we got it wrong.

This CL moves the deallocation of the AsyncCompileJob object to the
place where the promise which belongs to the AsyncCompileJob is either
resolved or rejected. This is a more appropriate place to deallocate the
object, because conceptionally, at the end of every an AsyncCompileJob
its promise should either be resolved or rejected.

R=clemensh@chromium.org, mtrofin@chromium.org

Change-Id: I87618c5619a3ac923645d1c3f6acaee9b0b14a83
Reviewed-on: https://chromium-review.googlesource.com/486884Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44896}