Remove net::CookieSameSite::DEFAULT_MODE enum value

Force callers to specify a SameSite mode instead of relying on defaults
which may be subject to change.

Also removes blink::WebCanonicalCookie::kDefaultSameSiteMode.

Bug: 953306
Change-Id: Iaea2224a28a169804048ad9f765e811374a9836f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1567955
Reviewed-by: Dmitry Gozman <[email protected]>
Reviewed-by: Mohammad Refaat <[email protected]>
Reviewed-by: Maks Orlovich <[email protected]>
Reviewed-by: David Roger <[email protected]>
Commit-Queue: Lily Chen <[email protected]>
Cr-Commit-Position: refs/heads/master@{#651750}
33 files changed