Remove guard for portals default activation

This portals behaviour change was guarded by a flag as we did not want
to change behaviour in the middle of an origin trial. The portals origin
trial lasted from M85 to M86, so we can now un-gate the change.

Bug: 1102081
Change-Id: I9202363c56bb2801874ccb84c16e1e6527a40e0a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2510373Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822725}

third_party/blink/renderer/core/html/portal/html_portal_element.cc

@@ -474,11 +474,9 @@ void HTMLPortalElement::RemovedFrom(ContainerNode& node) {
 }
 
 void HTMLPortalElement::DefaultEventHandler(Event& event) {
-  // Support the new behavior whereby clicking (or equivalent operations via
-  // keyboard and other input modalities) a portal element causes it to activate
-  // unless prevented.
-  if (RuntimeEnabledFeatures::PortalsDefaultActivationEnabled() &&
-      event.type() == event_type_names::kDOMActivate) {
+  // Clicking (or equivalent operations via keyboard and other input modalities)
+  // a portal element causes it to activate unless prevented.
+  if (event.type() == event_type_names::kDOMActivate) {
     ActivateDefault();
     event.SetDefaultHandled();
   }

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -1544,10 +1544,6 @@
       status: "test",
       origin_trial_feature_name: "Portals",
     },
-    {
-      name: "PortalsDefaultActivation",
-      status: "test",
-    },
     {
       name: "PreciseMemoryInfo",
     },