Callback screenshot to getContextualSearchState if token refresh is enabled.

As proposed in go/l2a-css, return the screenshot to the
getContextualSearchState callback. This is gated by the
token refresh flag in preparation for merging to mainline.

Flag: EXEMPT Rewrite.
Bug: 338598282
Test: Tested on device and with CTS
Change-Id: I715fa72e7058223f10bc4f67cb95ff3459671a3e