Fix initial search box position for app list view state transition

If app list view state transition is started during app list page
transition, the initial search box position should be calculated as a
position for the current app list page, otherwise the search box
will initially be misplaced.

BUG=999273

Change-Id: I053ab7f962b7c0a00914be97a0532f9ea445af42
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1824363


Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699977}