Add optional auto-dismiss for alerts, including alert followups

BUG=skia:3135

Review URL: https://codereview.chromium.org/733053006
Take the sk.get out of query-sk.

Have the params passed into the element via a setParamSet() method.

BUG=skia:

Review URL: https://codereview.chromium.org/736703002
Fix CSS for skiaperf.

Make the version link visible and clean up some
CSS by using /deep/ instead of ::shadow.

BUG=skia:

Review URL: https://codereview.chromium.org/734393002