Add flag for share wifi button.

One-pager: https://docs.google.com/document/d/185I0E8_J4ZZDEujJm7e1qIA5DRrdF0Pzy5Ix3dt_WA4/edit

Bug: b/294487249

Test: Manual test
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:5a330b785f2e2df67fe3684dbc60436a043a4285)
Merged-In: Ia63161f3658cbd6b5c9cca0a3848141d3add6658
Change-Id: Ia63161f3658cbd6b5c9cca0a3848141d3add6658