WebProcess sandbox all denies file:/// accesses after you navigate to a nonexistent file.
1) Go to a file: url that exists.
2) Go to another file: that doesn't exist
3) Try to go to a file: url that exists.
You won't be able to go to the file: url in step 3.
Created attachment 93387 [details]
Committed r86409: <http://trac.webkit.org/changeset/86409>