GitLab

This CL deactivates "Push dummy suggestion in 10 seconds" button in
snippets internals if either
1) listener is nullptr (e.g. feature is disabled)
2) listener is not listening.

Previously pressing the button when (1) holds lead to a crash, (2) - nothing
being pushed without any signal.

Bug: 771537
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I788c9d16e277890db97dde2ed7cea166f32a96f7
Reviewed-on: https://chromium-review.googlesource.com/699999
Commit-Queue: vitaliii <vitaliii@chromium.org>
Reviewed-by: Chris Pickel <sfiera@chromium.org>
Cr-Commit-Position: refs/heads/master@{#506704}