Set SupervisedUserCommittedInterstitials to enabled by default.

After testing on 50% of Dev/Canary/Beta and 1% of stable, no new bugs
seem to have appeared, so SupervisedUserCommittedInterstitials will be
launched at 100%

Bug: 755632
Change-Id: I8b8ebf8bfcebed57ca39cf0177d099280c2462c8
Reviewed-on: https://chromium-review.googlesource.com/1160879Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Carlos IL <carlosil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580370}

chrome/common/chrome_features.cc

@@ -556,7 +556,7 @@ const base::Feature kSoundContentSetting{"SoundContentSetting",
 // Enables or disabled committed interstitials for Supervised User
 // interstitials.
 const base::Feature kSupervisedUserCommittedInterstitials{
-    "SupervisedUserCommittedInterstitials", base::FEATURE_DISABLED_BY_DEFAULT};
+    "SupervisedUserCommittedInterstitials", base::FEATURE_ENABLED_BY_DEFAULT};
 
 #if defined(OS_CHROMEOS)
 // Enables or disables chrome://sys-internals.

testing/variations/fieldtrial_testing_config.json

@@ -4066,25 +4066,6 @@
             ]
         }
     ],
-    "SupervisedUserCommittedInterstitials": [
-        {
-            "platforms": [
-                "android",
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "SupervisedUserCommittedInterstitialsEnabled",
-                    "enable_features": [
-                        "SupervisedUserCommittedInterstitials"
-                    ]
-                }
-            ]
-        }
-    ],
     "TLS13Variant": [
         {
             "platforms": [