GitLab

Press 'Delete' or 'Backspace' key from keyboard will delete selected history items
on MD History.

BUG=627408
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2159773003
Cr-Commit-Position: refs/heads/master@{#406715}