Reproduction steps:
- Patch https://crrev.com/c/1293057 if it hasn't been committed
- Open badssl.com on ios-web-view-shell
- Tap the link "mixed"
- Add breakpoint on -[CWVWebView webStateDidChangeVisibleSecurityState:]
- Tap the browser back button

Expected:
- It breaks on the breakpoint because the navigation changes the security state (mixed content -> entirely HTTPS)

Actual:
- It does not break on the breakpoint. Note that it breaks on forward navigation between these pages.