Add chrome:flag for page info sharing

Bug: b/329099913
Change-Id: I28e57df68aa920a04ab10825e494fef1271ad2d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5416634


Reviewed-by: Siddhartha S <ssid@chromium.org>
Auto-Submit: Salvador Guerrero Ramos <salg@google.com>
Commit-Queue: Siddhartha S <ssid@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1281951}