Web UI: Autogenerate modulized FindShortcutBehavior

Autogenerate a JS module version of FindShortcutBehavior, its
dependencies (KeyboardShortcutList), and its browser test. This is a
prerequisite for migrating pages that depend on this behavior to
Polymer 3 (e.g. bookmarks).

Bug: 1022213
Change-Id: Ifbf2680c5f044474de68b11da9a434c96a13381e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1913510
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715102}
10 files changed