OK, looks like my last patch was not enough. I still got some crashes, and end up figuring we cannot trust in Page being alive or null, at all, so my alternative approach to the crash is to do explicit ref counting to guard the webView in between the clipboard call and its callbacks being called.
Created attachment 46713 [details] Use WebView object instead of page for clipboard callbacks, allowing us to avoid its destruction inbetween
*** This bug has been marked as a duplicate of bug 32900 ***
Comment on attachment 46713 [details] Use WebView object instead of page for clipboard callbacks, allowing us to avoid its destruction inbetween Unflagging since this appears to be already fixed in the original of which this is a duplicate.