Bug 1650089 - Part 5: Skip the unnecessary about:blank load when loading view-source for a document, r=Gijs

This load was causing a process switch after the changes in this patch.
This caused the view-source load to also process-switch back when loaded
and confused some view-source machinery. The load isn't necessary, and
if skipped the process switch due to navigation will not occur.

Differential Revision: https://phabricator.services.mozilla.com/D120736

browser/base/content/browser.js

@@ -3168,6 +3168,7 @@ async function BrowserViewSourceOfDocument(args) {
     preferredRemoteType,
     initialBrowsingContextGroupId,
     triggeringPrincipal: Services.scriptSecurityManager.getSystemPrincipal(),
+    skipLoad: true,
   });
   args.viewSourceBrowser = tabBrowser.getBrowserForTab(tab);
   top.gViewSourceUtils.viewSourceInBrowser(args);