This test checks that going back twice without committing doesn't corrupt the back/forward list.

If testing manually, click here.

============== Back Forward List ==============
curr->  http://127.0.0.1:8000/navigation/back-twice-without-commit.html  **nav target**
        http://127.0.0.1:8000/navigation/resources/back-twice-page-2.html  **nav target**
        http://127.0.0.1:8000/navigation/resources/back-twice-page-3.html  **nav target**
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