Bug 1960602 - More explicitly block bfcache when a subframe is loading. r=smaug

The test now passes with http2/http3 (where it didn't use to because the
frame was not OOP in that case).

Differential Revision: https://phabricator.services.mozilla.com/D245741

docshell/base/CanonicalBrowsingContext.cpp

@@ -2987,6 +2987,9 @@ static void LogBFCacheBlockingForDoc(BrowsingContext* aBrowsingContext,
   if (aBFCacheCombo & BFCacheStatus::ACTIVE_LOCK) {
     MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * has active Web Locks"));
   }
+  if (aBFCacheCombo & BFCacheStatus::PAGE_LOADING) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * has page loading"));
+  }
 }
 
 bool CanonicalBrowsingContext::AllowedInBFCache(

docshell/test/navigation/mochitest.toml

@@ -105,10 +105,6 @@ support-files = [
   "iframe_slow_onload.html",
   "iframe_slow_onload_inner.html",
 ]
-skip-if = [
-  "http3",
-  "http2",
-]
 
 ["test_bug13871.html"]
 skip-if = [

docshell/test/navigation/test_blockBFCache.html

@@ -98,7 +98,7 @@ const blockBFCacheTests = [
   },
 ];
 
-if (SpecialPowers.effectiveIsolationStrategy() == SpecialPowers.ISOLATION_STRATEGY.IsolateEverything) {
+if (SpecialPowers.Services.appinfo.sessionHistoryInParent) {
   blockBFCacheTests.push({
     name: "Loading OOP iframe",
     test: () => {