class WireServer

Populates or updates the cache of a font package, fetching it if it is not present on the

local system.

+ request `package_url` the package URL of a font package.

+ request `directory_request` a request for a directory that will be resolved when the

package has been successfully cached. The directory should contain a single file,

corresponding to the asset filename. The client should retain the directory handle

for as long as needed to prevent the package from being evicted from cache.

* error a zx_status value indicating failure. One of the following:

* `ZX_ERR_ACCESS_DENIED` if the resolver does not have permission to fetch a

package blob.

* `ZX_ERR_IO` if there is some other unspecified error during I/O.

* `ZX_ERR_NOT_FOUND` if the font package or a package blob does not exist, or is

not known to be a font package.

* `ZX_ERR_NO_SPACE` if there is no space available to store the package.

* `ZX_ERR_UNAVAILABLE` if the resolver is currently unable to fetch a package blob.

|bind_handler| returns a handler that binds incoming connections to this

server implementation.

The returned handler borrows the server instance.

The server must outlive the provided |dispatcher|. Only after

the dispatcher is shutdown will it be safe to destroy the servers.

The server should not be moved.