Launch back gesture refactor android

This CL only enables the flag. Cleaning will be followed.

Bug: 332956019
Change-Id: I9b084ab77c4f1f32baf9759a3b4b3f2179d4328e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5426491


Reviewed-by: Theresa Sullivan <twellington@chromium.org>
Commit-Queue: Lijin Shen <lazzzis@google.com>
Reviewed-by: Xi Han <hanxi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1283505}