Bug 1510490 - Add dependency on SHA2. r=mattwoodrow

Just pushing this down my patch queue to avoid triggering large cargo
rebuilds when rebasing.

Depends on D13438

Differential Revision: https://phabricator.services.mozilla.com/D13439

Cargo.lock

@@ -2956,6 +2956,7 @@ dependencies = [
  "rayon 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ron 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.80 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread_profiler 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.40 (registry+https://github.com/rust-lang/crates.io-index)",

gfx/wr/webrender/Cargo.toml

@@ -37,6 +37,7 @@ rayon = "1"
 ron = { optional = true, version = "0.1.7" }
 serde = { optional = true, version = "1.0", features = ["serde_derive"] }
 serde_json = { optional = true, version = "1.0" }
+sha2 = "0.7"
 smallvec = "0.6"
 thread_profiler = "0.1.1"
 time = "0.1"

gfx/wr/webrender/src/lib.rs

@@ -179,6 +179,7 @@ extern crate rayon;
 extern crate ron;
 #[cfg(feature = "debugger")]
 extern crate serde_json;
+extern crate sha2;
 extern crate smallvec;
 extern crate time;
 #[cfg(feature = "debugger")]