Remove use of UnescapeRule::URL_SPECIAL_CHARS from filesystem logic.
Remove use of UnescapeRule::URL_SPECIAL_CHARS from filesystem logic.

We're removing this, in favor of PATH_SEPARATORS and
URL_SPECIAL_CHARS_EXCEPT_PATH_SEPARATORS, to avoid any
security issues with this, going forward.

Permission checking is done in ParseFileSystemSchemeURL, so unescaping
them should be safe, though this is different from how file URLs are
handled.

BUG=589257

Review URL: https://codereview.chromium.org/1761083002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#379209}

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