Make onload async

Source/core/loader/NavigationScheduler.cpp

Index: Source/core/loader/NavigationScheduler.cpp
diff --git a/Source/core/loader/NavigationScheduler.cpp b/Source/core/loader/NavigationScheduler.cpp
index 2bb2bd6fa2bc93d59d3b926e6df27b947951b101..dfe02dd72e2e5f5fa8af765c1586df0aebcd5a5e 100644
--- a/Source/core/loader/NavigationScheduler.cpp
+++ b/Source/core/loader/NavigationScheduler.cpp
@@ -294,8 +294,11 @@ bool NavigationScheduler::mustLockBackForwardList(LocalFrame* targetFrame)
     // Navigation of a subframe during loading of an ancestor frame does not create a new back/forward item.
     // The definition of "during load" is any time before all handlers for the load event have been run.
     // See https://bugs.webkit.org/show_bug.cgi?id=14957 for the original motivation for this.
-    Frame* parentFrame = targetFrame->tree().parent();
-    return parentFrame && parentFrame->isLocalFrame() && !toLocalFrame(parentFrame)->loader().allAncestorsAreComplete();
+    for (Frame* parentFrame = targetFrame->tree().parent(); parentFrame; parentFrame = parentFrame->tree().parent()) {
+        if (!parentFrame->isLocalFrame() || !toLocalFrame(parentFrame)->document()->loadEventFinished())
+            return true;
+    }
+    return false;
 }
 
 void NavigationScheduler::scheduleLocationChange(Document* originDocument, const String& url, const Referrer& referrer, bool lockBackForwardList)