GitLab

This adds a command-line switch for Android Webview which toggles the
CookieManager's cookie access semantics to Non-legacy if the switch is
present. The current default is Legacy, which disables
SameSite-by-default (SSbD) and Schemeful Same-Site (SSS).

With the switch present, SSbD is enabled because it is enabled by
default in the content layer. The switch additionally enables the
base::Feature for SSS (currently disabled by default), so that it
enables both SSbD and SSS ("modern" behavior).

This also adds the switch to ProductionSupportedFlagList, so that it
can be toggled in the Flags UI.

Bug: 986319
Change-Id: I0ba85642cee03bf4284983b6f4c252a24bfd020a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2570073Reviewed-by: Maksim Orlovich <morlovich@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lily Chen <chlily@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834400}