Bug 1616353 - Part 6.2: Remove setOriginAttributesBeforeLoading API, r=smaug

This API is no longer possible to implement, as it will always try to set the
OriginAttributes on a content BrowsingContext after it has been attached, and JS
can never observe a detached BrowsingContext.

Users of this API are instead changed to perform assertions that
originAttributes have already been set correctly.

Differential Revision: https://phabricator.services.mozilla.com/D67046

docshell/base/nsDocShell.cpp

@@ -12546,21 +12546,6 @@ nsresult nsDocShell::SetOriginAttributes(const OriginAttributes& aAttrs) {
   return mBrowsingContext->SetOriginAttributes(aAttrs);
 }
 
-NS_IMETHODIMP
-nsDocShell::SetOriginAttributesBeforeLoading(
-    JS::Handle<JS::Value> aOriginAttributes, JSContext* aCx) {
-  if (!aOriginAttributes.isObject()) {
-    return NS_ERROR_INVALID_ARG;
-  }
-
-  OriginAttributes attrs;
-  if (!attrs.Init(aCx, aOriginAttributes)) {
-    return NS_ERROR_INVALID_ARG;
-  }
-
-  return SetOriginAttributes(attrs);
-}
-
 NS_IMETHODIMP
 nsDocShell::ResumeRedirectedLoad(uint64_t aIdentifier, int32_t aHistoryIndex) {
   RefPtr<nsDocShell> self = this;