Auto merge of #17738 - jdm:no-css-text, r=bholley

Don't retrieve the CSS source when a parse error is reported.

Per https://bugzilla.mozilla.org/show_bug.cgi?id=1381045 retrieving the CSS source is an unnecessary performance hit for Stylo.

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because they are tested by Gecko.

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ports/geckolib/error_reporter.rs

@@ -299,7 +299,8 @@ impl ParseErrorReporter for ErrorReporter {
 
         let name = error.to_gecko_message();
         let param = error.error_param().into_str();
-        let source = input.current_line();
+        // The CSS source text is unused and will be removed in bug 1381188.
+        let source = "";
         unsafe {
             Gecko_ReportUnexpectedCSSError(self.0,
                                            name.as_ptr() as *const _,