Auto merge of #18710 - mhaessig:remove-rustc-serialize, r=jdm

Replace rustc_serialize with serde_json in style_tests

#12410 Stop using rustc_serialize

Replaced rustc_serialize with serde_json in
- [ ] ~~components/config/Cargo.toml~~
- [ ] ~~components/config/lib.rs~~
- [ ] ~~components/config/prefs.rs~~
- [ ] ~~components/script_traits/Cargo.toml~~
- [ ] ~~components/script_traits/lib.rs~~
- [ ] ~~components/script_traits/webdriver_msg.rs~~
- [ ] ~~components/webdriver_server/Cargo.toml~~
- [ ] ~~components/webdriver_server/lib.rs~~
- [X] tests/unit/style/Cargo.toml
- [X] test/unit/style/lib.rs
- [X] test/unit/style/properties/scaffolding.rs

PR checks:
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [X] These changes fix (partially) #12410.
- [X] These changes do not require tests because functionality was not changed or a test itself was edited

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tests/unit/style/Cargo.toml

@@ -17,7 +17,7 @@ euclid = "0.15"
 html5ever = "0.21"
 parking_lot = "0.4"
 rayon = "0.8"
-rustc-serialize = "0.3"
+serde_json = "1.0"
 selectors = {path = "../../../components/selectors"}
 servo_arc = {path = "../../../components/servo_arc"}
 servo_atoms = {path = "../../../components/atoms"}

tests/unit/style/lib.rs

@@ -11,8 +11,8 @@ extern crate euclid;
 #[macro_use] extern crate html5ever;
 extern crate parking_lot;
 extern crate rayon;
-extern crate rustc_serialize;
 extern crate selectors;
+extern crate serde_json;
 extern crate servo_arc;
 extern crate servo_atoms;
 extern crate servo_config;

tests/unit/style/properties/scaffolding.rs

@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use rustc_serialize::json::Json;
+use serde_json::{self, Value};
 use std::env;
 use std::fs::{File, remove_file};
 use std::path::Path;
@@ -25,10 +25,11 @@ fn properties_list_json() {
         .status()
         .unwrap();
     assert!(status.success());
-    let properties = Json::from_reader(&mut File::open(json).unwrap()).unwrap();
+
+    let properties: Value = serde_json::from_reader(File::open(json).unwrap()).unwrap();
     assert!(properties.as_object().unwrap().len() > 100);
-    assert!(properties.find("margin").is_some());
-    assert!(properties.find("margin-top").is_some());
+    assert!(properties.as_object().unwrap().contains_key("margin"));
+    assert!(properties.as_object().unwrap().contains_key("margin-top"));
 }
 
 #[cfg(windows)]