Enable WKHTTPSystemCookieStore usage by default.

Targeted to ramp up launch on M75, enabling it by default for M76

Bug: 779106
Change-Id: I137cdc3e96e383a876aeb0a0330dc8140c88edd5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1635074Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mohammad Refaat <mrefaat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664762}

ios/web/common/features.mm

@@ -25,7 +25,7 @@ const base::Feature kStorePendingItemInContext{
     "StorePendingItemInContext", base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kWKHTTPSystemCookieStore{"WKHTTPSystemCookieStore",
-                                             base::FEATURE_DISABLED_BY_DEFAULT};
+                                             base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kCrashOnUnexpectedURLChange{
     "CrashOnUnexpectedURLChange", base::FEATURE_ENABLED_BY_DEFAULT};