[NTP] Mobile friendly buttons on snippets internals.

Previously the buttons were very wide, but not high enough. Moreover, some were too close to each other.

Please see screenshots in the bug.

BUG=724080
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2893933002
Cr-Commit-Position: refs/heads/master@{#473857}
2 files changed