Auto merge of #196 - jdm:surfmanup, r=asajeffrey

Update surfman and surfman-chains.

Author: bors-servo

webxr/Cargo.toml

@@ -43,8 +43,8 @@ gvr-sys = { version = "0.7", optional = true }
 openxr = { git = "https://github.com/servo/openxrs.git", branch="secondary-views-2", optional = true }
 serde = { version = "1.0", optional = true }
 sparkle = "0.1"
-surfman = "0.3"
-surfman-chains = "0.5"
+surfman = "0.4"
+surfman-chains = "0.6"
 time = "0.1.42"
 
 [target.'cfg(target_os = "windows")'.dependencies]