Bug 1578623 use an opaque origin for WorkletGlobalScope r=baku

The environment settings object for a WorkletGlobalScope derives from the
relevant settings object of the main-thread Worklet object, but the origin is
a unique opaque origin.
https://drafts.css-houdini.org/worklets/#set-up-a-worklet-environment-settings-object

Depends on D44775

Differential Revision: https://phabricator.services.mozilla.com/D44776

--HG--
extra : moz-landing-system : lando

dom/worklet/WorkletImpl.cpp

@@ -10,6 +10,7 @@
 #include "WorkletThread.h"
 
 #include "mozilla/BasePrincipal.h"
+#include "mozilla/NullPrincipal.h"
 #include "mozilla/dom/RegisterWorkletBindings.h"
 #include "mozilla/dom/ScriptSettings.h"
 #include "mozilla/dom/WorkletBinding.h"
@@ -35,7 +36,7 @@ WorkletLoadInfo::WorkletLoadInfo(nsPIDOMWindowInner* aWindow)
 
 WorkletImpl::WorkletImpl(nsPIDOMWindowInner* aWindow, nsIPrincipal* aPrincipal)
     : mOriginAttributes(BasePrincipal::Cast(aPrincipal)->OriginAttributesRef()),
-      mPrincipal(aPrincipal),
+      mPrincipal(NullPrincipal::CreateWithInheritedAttributes(aPrincipal)),
       mWorkletLoadInfo(aWindow),
       mTerminated(false) {}