vmo_get_size - read the current size of a VMO object
#include <zircon/syscalls.h>
zx_status_t zx_vmo_get_size(zx_handle_t handle, uint64_t* size);
zx_vmo_get_size() returns the current size of the VMO.
TODO(ZX-2399)
zx_vmo_get_size() returns ZX_OK on success. In the event
of failure, a negative error value is returned.
ZX_ERR_BAD_HANDLE handle is not a valid handle.
ZX_ERR_WRONG_TYPE handle is not a VMO handle.
ZX_ERR_INVALID_ARGS size is an invalid pointer or NULL.