GitLab

Specifically:
 - Replace MockInteractions.tap() with a click() call.
 - Replace Polymer.Base.create() with document.createElement().

This is in preparation of migrating to Polymer3, where every dependency needs to
be imported as a module.

Bug: 1005029
Change-Id: I87b07d59b69df69258b2d7a1492cea014e053768
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1819678Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699063}