Keep track in the browser of which frames have onunload and onbeforeunload handlers.

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 921ece3ec8a7e47f39bdfae3480d418ef9b0184f..1f5657a8edd3fb29d58bf79f689ff067fb13a8de 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -1422,7 +1422,9 @@ void WebContentsImpl::WasUnOccluded() {
 bool WebContentsImpl::NeedToFireBeforeUnload() {
   // TODO(creis): Should we fire even for interstitial pages?
   return WillNotifyDisconnection() && !ShowingInterstitialPage() &&
-         !GetRenderViewHost()->SuddenTerminationAllowed();
+         !GetRenderViewHost()->SuddenTerminationAllowed() &&
+         (GetMainFrame()->ShouldDispatchBeforeUnload() ||
+          GetMainFrame()->ShouldDispatchUnload());

[nasko, 2017/03/29 23:31:26]

This seems very very broken. Let's put a TODO to clean this up as it is
incorrect/inconsistent. Feel free to have it TODO(nasko) ;).

[jam, 2017/03/30 14:53:23]

Done.

 }
 
 void WebContentsImpl::DispatchBeforeUnload() {