Add Schemeful Same-Site experimental-cookie-features flag

Modify --enable-experimental-cookie-features to also enable
kSameSiteByDefaultCookies.

Bug: 1030938
Change-Id: I31a533009d28b79dddd2c7e3cee238e76ccb995d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2342209Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Steven Bingler <bingler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797823}

content/public/common/content_switch_dependent_feature_overrides.cc

@@ -78,7 +78,9 @@ GetSwitchDependentFeatureOverrides(const base::CommandLine& command_line) {
       {switches::kEnableExperimentalCookieFeatures,
        std::cref(net::features::kSameSiteDefaultChecksMethodRigorously),
        base::FeatureList::OVERRIDE_ENABLE_FEATURE},
-      // TODO(crbug.com/1030938): Add Schemeful Same-Site.
+      {switches::kEnableExperimentalCookieFeatures,
+       std::cref(net::features::kSchemefulSameSite),
+       base::FeatureList::OVERRIDE_ENABLE_FEATURE},
   };
 
   std::vector<base::FeatureList::FeatureOverrideInfo> overrides;