Bug 1547057 - HTMLIFrameElement must always set the default origin for FeaturePolicy, r=ckerschb

Differential Revision: https://phabricator.services.mozilla.com/D29002

dom/html/HTMLIFrameElement.cpp

@@ -55,6 +55,10 @@ HTMLIFrameElement::HTMLIFrameElement(
     : nsGenericHTMLFrameElement(std::move(aNodeInfo), aFromParser) {
   // We always need a featurePolicy, even if not exposed.
   mFeaturePolicy = new FeaturePolicy(this);
+
+  nsCOMPtr<nsIPrincipal> origin = GetFeaturePolicyDefaultOrigin();
+  MOZ_ASSERT(origin);
+  mFeaturePolicy->SetDefaultOrigin(origin);
 }
 
 HTMLIFrameElement::~HTMLIFrameElement() {}