WebProcess sandbox all denies file:/// accesses after you navigate to a nonexistent file.
To reproduce: 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] Patch
Committed r86409: <http://trac.webkit.org/changeset/86409>