edition: Remove extern crate lines

In Rust 2018 edition, `extern crate` is no longer required for importing
from other crates. Instead of writing:

    extern crate dep;
    use dep::Thing;

we write:

    use dep::Thing;

In this approach, macros are imported individually from the declaring
crate rather than through #[macro_use]. Before:

    #[macro_use]
    extern crate sys_util;

After:

    use sys_util::{debug, error};

The only place that `extern crate` continues to be required is in
importing the compiler's proc_macro API into a procedural macro crate.
This will hopefully be fixed in a future Rust release.

    extern crate proc_macro;

TEST=cargo check
TEST=cargo check --all-features
TEST=cargo check --target aarch64-unknown-linux-gnu
TEST=local kokoro

Change-Id: I0b43768c0d81f2a250b1959fb97ba35cbac56293
Reviewed-on: https://chromium-review.googlesource.com/1565302
Commit-Ready: David Tolnay <dtolnay@chromium.org>
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: David Tolnay <dtolnay@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: David Tolnay <dtolnay@chromium.org>

1 files changed, 0 insertions, 6 deletions

diff --git a/resources/src/lib.rs b/resources/src/lib.rs
index f300e0e..602c390 100644
--- a/resources/src/lib.rs
+++ b/resources/src/lib.rs
@@ -4,12 +4,6 @@
 
 //! Manages system resources that can be allocated to VMs and their devices.
 
-#[cfg(feature = "wl-dmabuf")]
-extern crate gpu_buffer;
-extern crate libc;
-extern crate msg_socket;
-extern crate sys_util;
-
 mod address_allocator;
 mod gpu_allocator;
 mod system_allocator;