Thumbnail capturing: Disable features by default

The previous launch was aborted, let's start over fresh for M64.

Bug: 718413
Change-Id: I4bdfc074c57051d20150e9352178acc0c1ee81ac
Reviewed-on: https://chromium-review.googlesource.com/781759


Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#518271}