Ensure runtime enabled features are enabled as part of activating navigation trials.

2 small fixes for OriginTrialContext:
* only exit early from InitializePendingFeatures if there are
  no enabled features, and no navigation features
* ensure OriginTrialContext::IsFeatureEnabled (which is invoked
  via RuntimeEnabledFeatures, for OT features) returns true if
  a feature was activated via navigation.

These were discovered while writing tests as part of
https://chromium-review.googlesource.com/c/chromium/src/+/1601980.


Change-Id: Ia8e711ab61dc4bf14a6e3c12a52faf5e1f096bec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1618175Reviewed-by: Ian Clelland <iclelland@chromium.org>
Commit-Queue: Bryan McQuade <bmcquade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662935}

third_party/blink/renderer/core/origin_trials/origin_trial_context.cc

@@ -240,7 +240,7 @@ void OriginTrialContext::ActivateNavigationFeaturesFromInitiator(
 }
 
 void OriginTrialContext::InitializePendingFeatures() {
-  if (!enabled_features_.size())
+  if (!enabled_features_.size() && !navigation_activated_features_.size())
     return;
   auto* document = DynamicTo<Document>(GetSupplementable());
   if (!document)
@@ -279,8 +279,10 @@ bool OriginTrialContext::IsFeatureEnabled(OriginTrialFeature feature) const {
   if (!RuntimeEnabledFeatures::OriginTrialsEnabled())
     return false;
 
-  if (enabled_features_.Contains(feature))
+  if (enabled_features_.Contains(feature) ||
+      navigation_activated_features_.Contains(feature)) {
     return true;
+  }
 
   // HTML imports do not have a browsing context, see:
   //  - Spec: https://w3c.github.io/webcomponents/spec/imports/#terminology