Unless SELinux blocks it, all apps have identical access to files
included on the system partition. Since there are a handful of
useful files stored there, like ringtones and license files, carve
out an exception to allow file:///system/ style paths.
Note that StrictMode isn't a security mechanism, which is why we're
not concerned about resolving canonical paths.
Bug: 26895798
Change-Id: If0b659d30c4e51377edcf01445392759d1e4962e
ac3be9a283