toolchain: Update to Rust 1.31.0

We updated the production toolchain from 1.30 to 1.31 in CL:1366446.
This CL does the same upgrade for the local developer toolchain and
Kokoro.

The relevant changes are in rust-toolchain and kokoro/Dockerfile.
The rest are from rustfmt.

TEST=cargo fmt --all -- --check
TEST=as described in kokoro/README.md

Change-Id: I3b4913f3e237baa36c664b4953be360c09efffd4
Reviewed-on: https://chromium-review.googlesource.com/1374376
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: David Tolnay <dtolnay@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/devices/src/bus.rs b/devices/src/bus.rs
index 8bee1d0..8124d87 100644
--- a/devices/src/bus.rs
+++ b/devices/src/bus.rs
@@ -111,7 +111,8 @@ impl Bus {
                     len: 1,
                     full_addr: false,
                 },
-            ).rev()
+            )
+            .rev()
             .next()?;
         Some((*range, dev))
     }
@@ -160,7 +161,8 @@ impl Bus {
                     full_addr,
                 },
                 device,
-            ).is_some()
+            )
+            .is_some()
         {
             return Err(Error::Overlap);
         }