WebUI: remove paper-icon-button from third_party/polymer

Bug: 960564
Change-Id: Iee43b2f172c145a4598450de3d1d09d7719f45ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1625917
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Esmael El-Moslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662434}
8 files changed