[Android] Add entry point for tests that already started in a blank page

Bug: None
Change-Id: Ia77d3b5ab03bdb0b8658e0e8b5e5e6ab158a671a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5617752


Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1313027}