GitLab

For these functions the default no-op behavior is fine, so remove the calls
to NOTIMPLEMENTED to reduce log spam.

BUG=none
TEST=none
TBR=yoz@chromium.org for changing a comment in extensions/

Review URL: https://codereview.chromium.org/587913002

Cr-Commit-Position: refs/heads/master@{#295836}