Bug 1597154 - pt 1. Avoid redirecting loads between processes more th…

…an once r=mattwoodrow,kmag

This doesn't fix the bug, but it is a good idea.

Differential Revision: https://phabricator.services.mozilla.com/D57597

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

docshell/base/nsDocShell.cpp

@@ -8981,9 +8981,10 @@ nsresult nsDocShell::InternalLoad(nsDocShellLoadState* aLoadState,
   }
 
   // Check if the webbrowser chrome wants the load to proceed; this can be
-  // used to cancel attempts to load URIs in the wrong process.
+  // used to cancel attempts to load URIs in the wrong process. use
+  // GetPendingRedirectedChannel() to avoid revisiting a redirect decision.
   nsCOMPtr<nsIWebBrowserChrome3> browserChrome3 = do_GetInterface(mTreeOwner);
-  if (browserChrome3) {
+  if (browserChrome3 && !aLoadState->GetPendingRedirectedChannel()) {
     bool shouldLoad;
     rv = browserChrome3->ShouldLoadURI(
         this, aLoadState->URI(), aLoadState->GetReferrerInfo(),