[TreesInViz] Enable the feature by default.

We hold back on Linux to ensure test coverage on current path for at
least one platform.

Ready to move it to 50% beta.

TEST=bots

Bug: 369883417
Include-Ci-Only-Tests: true
Change-Id: I978dbe7e1c1af4ae2ae9b6064f130f2361cdfd4b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7830477
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Zhenyao Mo <zmo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1628275}
NOKEYCHECK=True
GitOrigin-RevId: b6929d00d568c847ded27caa2b3738637cba354f