MD History: Fix text selection in history items

Clicking on a history item would immediately change focus if the item
wasn't selected, preventing selection with the mouse. This fixes the
issue by preventing the extra unnecessary change of focus.

BUG=675058
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2962103002
Cr-Commit-Position: refs/heads/master@{#483632}
1 file changed