Auto merge of #18512 - tromey:preserve-style-sheet-source-url, r=SimonSapin

Preserve sourceURL comment on style sheets

In addition to the sourceMappingURL comment, there is a second special
comment, "sourceURL", that can be used to set the "display name" of a
style sheet for developer tools.  This name is also used as the base
URL for the source-map URL resolution algorithm.  sourceURL is
described here:
https://blog.getfirebug.com/2009/08/11/give-your-eval-a-name-with-sourceurl/
The devtools feature bug is here:
https://bugzilla.mozilla.org/show_bug.cgi?id=880831

This patch changes servo to preserve and expose this value for use in M-C.

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- [ ] These changes fix #__ (github issue number if applicable).

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ports/geckolib/Cargo.toml

@@ -15,7 +15,7 @@ gecko_debug = ["style/gecko_debug"]
 
 [dependencies]
 atomic_refcell = "0.1"
-cssparser = "0.21.0"
+cssparser = "0.21.1"
 env_logger = {version = "0.4", default-features = false} # disable `regex` to reduce code size
 libc = "0.2"
 log = {version = "0.3.5", features = ["release_max_level_info"]}

ports/geckolib/glue.rs

@@ -1124,6 +1124,18 @@ pub extern "C" fn Servo_StyleSheet_GetSourceMapURL(
     }
 }
 
+#[no_mangle]
+pub extern "C" fn Servo_StyleSheet_GetSourceURL(
+    sheet: RawServoStyleSheetContentsBorrowed,
+    result: *mut nsAString
+) {
+    let contents = StylesheetContents::as_arc(&sheet);
+    let url_opt = contents.source_url.read();
+    if let Some(ref url) = *url_opt {
+        write!(unsafe { &mut *result }, "{}", url).unwrap();
+    }
+}
+
 fn read_locked_arc<T, R, F>(raw: &<Locked<T> as HasFFI>::FFIType, func: F) -> R
     where Locked<T>: HasArcFFI, F: FnOnce(&T) -> R
 {