Use touchless 'add to homescreen' dialog for explore

Bug: 963516
Change-Id: If52da6c0d3c9b1a68e48a1e6ac39d6e785b44126
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1618032
Reviewed-by: Justin DeWitt <dewittj@chromium.org>
Commit-Queue: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661374}
4 files changed