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/gpu_display/src/lib.rs b/gpu_display/src/lib.rs
index da9d473..6b93bbc 100644
--- a/gpu_display/src/lib.rs
+++ b/gpu_display/src/lib.rs
@@ -219,7 +219,8 @@ impl GpuDisplay {
         let buffer_size = round_up_to_page_size(fb_size as usize * BUFFER_COUNT);
         let mut buffer_shm = SharedMemory::new(Some(
             CStr::from_bytes_with_nul(b"GpuDisplaySurface\0").unwrap(),
-        )).map_err(GpuDisplayError::CreateShm)?;
+        ))
+        .map_err(GpuDisplayError::CreateShm)?;
         buffer_shm
             .set_size(buffer_size as u64)
             .map_err(GpuDisplayError::SetSize)?;
@@ -273,7 +274,8 @@ impl GpuDisplay {
             .get_slice(
                 (buffer_index * surface.buffer_size) as u64,
                 surface.buffer_size as u64,
-            ).ok()
+            )
+            .ok()
     }
 
     /// Commits any pending state for the identified surface.