Reland "Remove SoleIntegration flag"

This is a reland of bfd17e5e46cad8a9aa563a627e3d492ef78aa836

The downstream dependency removal has been rolled.

Original change's description:
> Remove SoleIntegration flag
>
> Sole integration was launched in M65, and we no longer need this flag.
>
> Bug: 778805
> Change-Id: I6669a87dcb7a6ff4705a30aaa2cf71d6670a822a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1578101
> Commit-Queue: Wei-Yin Chen (陳威尹) <[email protected]>
> Reviewed-by: Theresa <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#653718}

Bug: 778805
Change-Id: Ifccdbe470d7444c07dc29ba509bb105ca741ad4f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1594803
Reviewed-by: Theresa <[email protected]>
Commit-Queue: Wei-Yin Chen (陳威尹) <[email protected]>
Cr-Commit-Position: refs/heads/master@{#656484}
8 files changed