Improve timer alignment code when timer duration is near the alignment interval.

BUG=259680
R=esprehn@chromium.org,jamesr@chromium.org

Review URL: https://chromiumcodereview.appspot.com/19847002

git-svn-id: svn://svn.chromium.org/blink/trunk@155190 bbb929c8-8fbe-4397-9dbb-9b2b20218538