Turn a bunch of ASSERTs into graceful failures when compiling listeners

Turn a bunch of ASSERTs into graceful failures when compiling listeners

BUG=456192
R=yangguo@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=189796

[dcarney, 2015-02-09 10:02:46]

dcarney@chromium.org changed reviewers:
+ dcarney@chromium.org

[dcarney, 2015-02-09 10:02:46]

lgtm

[jochen (gone - plz use gerrit), 2015-02-09 10:07:23]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-02-09 10:08:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/906193002/20001

[Yang, 2015-02-09 10:18:32]

On 2015/02/09 10:08:31, I haz the power (commit-bot) wrote:
> CQ is trying da patch. Follow status at
>  https://chromium-cq-status.appspot.com/patch-status/906193002/20001

lgtm.

[haraken, 2015-02-09 11:23:59]

LGTM

[commit-bot: I haz the power, 2015-02-09 12:26:03]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-02-09 12:26:03]

Try jobs failed on following builders:
  win_gpu on tryserver.chromium.gpu (JOB_TIMED_OUT,
http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu/builds/12...)
Timed out jobs are not retried to avoid causing additional load on the builders
with large pending queues.

[jochen (gone - plz use gerrit), 2015-02-09 12:32:14]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-02-09 12:33:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/906193002/20001

[commit-bot: I haz the power, 2015-02-09 13:29:45]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=189796