servo: Merge #19527 - Fix running `cargo test` at the repository root (from servo:root); r=SimonSapin

Source-Repo: https://github.com/servo/servo
Source-Revision: 8a8c06ac7b77ca1199c778f2ab6f1c27d88a340a

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 9788f0e00ebfa0724aa3d910efda8dcb367969c7

servo/tests/unit/style/properties/scaffolding.rs

@@ -10,7 +10,7 @@ use std::process::Command;
 
 #[test]
 fn properties_list_json() {
-    let top = Path::new(file!()).parent().unwrap().join("..").join("..").join("..").join("..");
+    let top = Path::new(&env::var("CARGO_MANIFEST_DIR").unwrap()).join("..").join("..").join("..");
     let json = top.join("target").join("doc").join("servo").join("css-properties.json");
     if json.exists() {
         remove_file(&json).unwrap()
@@ -24,7 +24,7 @@ fn properties_list_json() {
         .arg("regular")
         .status()
         .unwrap();
-    assert!(status.success());
+    assert!(status.success(), "{:?}", status);
 
     let properties: Value = serde_json::from_reader(File::open(json).unwrap()).unwrap();
     assert!(properties.as_object().unwrap().len() > 100);