GitLab

When firing the completion event make sure the document exists before
we try to get the rendered buffer that needs to be returned.

Bug: 751377
Change-Id: Id956f5a287b6b91b7bad04d85b6c8f3c32c9470d
Reviewed-on: https://chromium-review.googlesource.com/598727Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Commit-Queue: Hongchan Choi <hongchan@chromium.org>
Commit-Queue: Raymond Toy <rtoy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491527}