Bug 1778510: Require subclasses of nsIGlobalObject implement ShouldRFP r=asuth

For the less common subclasses we will hardcode a choice to always obey
RFP if the pref is enabled.

Differential Revision: https://phabricator.services.mozilla.com/D157562

dom/base/nsGlobalWindowInner.cpp

@@ -1629,7 +1629,9 @@ bool nsGlobalWindowInner::ShouldResistFingerprinting() const {
   if (mDoc) {
     return mDoc->ShouldResistFingerprinting();
   }
-  return nsIScriptGlobalObject::ShouldResistFingerprinting();
+  return nsContentUtils::ShouldResistFingerprinting(
+      "If we do not have a document then we do not have any context"
+      "to make an informed RFP choice, so we fall back to the global pref");
 }
 
 OriginTrials nsGlobalWindowInner::Trials() const {