edition: Eliminate ref keyword

As described in:
https://doc.rust-lang.org/edition-guide/rust-2018/ownership-and-lifetimes/default-match-bindings.html
which also covers the new mental model that the Rust Book will use for
teaching binding modes and has been found to be more friendly for both
beginners and experienced users.

Before:

    match *opt {
        Some(ref v) => ...,
        None => ...,
    }

After:

    match opt {
        Some(v) => ...,
        None => ...,
    }

TEST=cargo check --all-features
TEST=local kokoro

Change-Id: I3c5800a9be36aaf5d3290ae3bd3116f699cb00b7
Reviewed-on: https://chromium-review.googlesource.com/1566669
Commit-Ready: David Tolnay <dtolnay@chromium.org>
Tested-by: David Tolnay <dtolnay@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/devices/src/virtio/net.rs b/devices/src/virtio/net.rs
index a492561..d7de639 100644
--- a/devices/src/virtio/net.rs
+++ b/devices/src/virtio/net.rs
@@ -435,11 +435,11 @@ where
     fn keep_fds(&self) -> Vec<RawFd> {
         let mut keep_fds = Vec::new();
 
-        if let Some(ref tap) = self.tap {
+        if let Some(tap) = &self.tap {
             keep_fds.push(tap.as_raw_fd());
         }
 
-        if let Some(ref workers_kill_evt) = self.workers_kill_evt {
+        if let Some(workers_kill_evt) = &self.workers_kill_evt {
             keep_fds.push(workers_kill_evt.as_raw_fd());
         }