Bug 1721217 - Part 7: Make sure to cancel loads when a canonical BC gets discarded, r=nika

This fixes failures in browser/base/content/test/tabPrompts/browser_contentOrigins.js

Differential Revision: https://phabricator.services.mozilla.com/D126847

docshell/base/CanonicalBrowsingContext.cpp

@@ -1149,6 +1149,10 @@ void CanonicalBrowsingContext::CanonicalDiscard() {
     mTabMediaController = nullptr;
   }
 
+  if (mCurrentLoad) {
+    mCurrentLoad->Cancel(NS_BINDING_ABORTED);
+  }
+
   if (mWebProgress) {
     RefPtr<BrowsingContextWebProgress> progress = mWebProgress;
     progress->ContextDiscarded();