Bug 1711729 - Make browser/components/search/test/browser/browser_search_telemetry_sources_ads.js pass with Fission+BFCache by marking bfcache loads coming from shistory, r=peterv

With the patch the correct flag is passed up to here https://searchfox.org/mozilla-central/rev/6e630edb09c3ab06d0103665b16c9ea7dce782c5/browser/components/search/SearchSERPTelemetry.jsm#233-234

Differential Revision: https://phabricator.services.mozilla.com/D115639

docshell/base/nsDocShell.cpp

@@ -1216,6 +1216,7 @@ void nsDocShell::FirePageHideShowNonRecursive(bool aShow) {
 
       nsCOMPtr<nsIChannel> channel = doc->GetChannel();
       if (channel) {
+        SetLoadType(LOAD_HISTORY);
         SetCurrentURI(doc->GetDocumentURI(), channel,
                       /* aFireOnLocationChange */ true,
                       /* aIsInitialAboutBlank */ false, /* aLocationFlags */ 0);