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, 6 insertions, 3 deletions

diff --git a/tests/plugins.rs b/tests/plugins.rs
index 27bbc47..20adcab 100644
--- a/tests/plugins.rs
+++ b/tests/plugins.rs
@@ -36,7 +36,8 @@ fn get_target_path() -> PathBuf {
         .map(|mut path| {
             path.pop();
             path
-        }).expect("failed to get crosvm binary directory")
+        })
+        .expect("failed to get crosvm binary directory")
 }
 
 fn get_crosvm_path() -> PathBuf {
@@ -48,7 +49,8 @@ fn get_crosvm_path() -> PathBuf {
                 path.pop();
             }
             path
-        }).expect("failed to get crosvm binary directory")
+        })
+        .expect("failed to get crosvm binary directory")
 }
 
 fn build_plugin(src: &str) -> RemovePath {
@@ -98,7 +100,8 @@ fn run_plugin(bin_path: &Path, with_sandbox: bool) {
         "--seccomp-policy-dir",
         "tests",
         "--plugin",
-    ]).arg(
+    ])
+    .arg(
         bin_path
             .canonicalize()
             .expect("failed to canonicalize plugin path"),