Enable heavy ad intervention by default

Enables intervention by default in the Chrome binary, and removes
it's associated testing config which is no longer needed.

Bug: 959849
Change-Id: I5963aebd84894a94d37af053a99b8050394f3426
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2535550Reviewed-by: Josh Karlin <jkarlin@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: John Delaney <johnidel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827442}

chrome/common/chrome_features.cc

@@ -464,7 +464,7 @@ const base::Feature kHappinessTrackingSystem{"HappinessTrackingSystem",
 // Enables or disables the intervention that unloads ad iframes with intensive
 // resource usage.
 const base::Feature kHeavyAdIntervention{"HeavyAdIntervention",
-                                         base::FEATURE_DISABLED_BY_DEFAULT};
+                                         base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enables or disables reporting on the intervention that unloads ad iframes
 // with intensive resource usage.

testing/variations/fieldtrial_testing_config.json

@@ -3213,25 +3213,6 @@
             ]
         }
     ],
-    "HeavyAdIntervention": [
-        {
-            "platforms": [
-                "android",
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "HeavyAdIntervention"
-                    ]
-                }
-            ]
-        }
-    ],
     "HideAutofillSuggestions": [
         {
             "platforms": [