Enable futures io-compat feature

Change-Id: I5db2e6fb91cf7e39a04410a7e48d2a2697553b6c
diff --git a/rustc_deps/Cargo.lock b/rustc_deps/Cargo.lock
index 6297fef..5bc766b 100644
--- a/rustc_deps/Cargo.lock
+++ b/rustc_deps/Cargo.lock
@@ -515,12 +515,14 @@
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "either 1.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures 0.1.25 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures-channel-preview 0.3.0-alpha.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures-core-preview 0.3.0-alpha.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures-io-preview 0.3.0-alpha.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures-sink-preview 0.3.0-alpha.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "pin-utils 0.1.0-alpha.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "slab 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-io 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
diff --git a/rustc_deps/Cargo.toml b/rustc_deps/Cargo.toml
index 002f18c..d1cb259 100644
--- a/rustc_deps/Cargo.toml
+++ b/rustc_deps/Cargo.toml
@@ -21,7 +21,7 @@
 euclid = "0.19"
 failure = "0.1.1"
 font-rs = "0.1.3"
-futures-preview = "=0.3.0-alpha.9"
+futures-preview = { version = "=0.3.0-alpha.9", features = ["io-compat"] }
 getopts = "0.2"
 hex = "0.3.2"
 hyper = { version = "0.12.13", default-features = false }