Remove the url! plugin.

In rust-url 1.0 the `Url` struct is going to have private fields, and there
is no way to to create an aribitrary one without going through the parser.

The plugin never had a clear demonstrated performance benefit,
it was made mostly because it was possible and relatively easy at the time.

components/style/font_face.rs

@@ -102,7 +102,7 @@ fn parse_one_src(context: &ParserContext, input: &mut Parser) -> Result<Source,
     }
     let url = try!(input.expect_url());
     let url = context.base_url.join(&url).unwrap_or_else(
-        |_error| url!("about:invalid"));
+        |_error| Url::parse("about:invalid").unwrap());
 
     // Parsing optional format()
     let format_hints = if input.try(|input| input.expect_function_matching("format")).is_ok() {

components/style/parser.rs

@@ -34,7 +34,7 @@ impl<'a> ParserContext<'a> {
 impl<'a> ParserContext<'a> {
     pub fn parse_url(&self, input: &str) -> Url {
         self.base_url.join(input)
-            .unwrap_or_else(|_| url!("about:invalid"))
+            .unwrap_or_else(|_| Url::parse("about:invalid").unwrap())
     }
 }
 

components/style/selector_matching.rs

@@ -69,7 +69,7 @@ lazy_static! {
             Ok(res) => {
                 Stylesheet::from_bytes(
                     &res,
-                    url!("chrome:///quirks-mode.css"),
+                    Url::parse("chrome:///quirks-mode.css").unwrap(),
                     None,
                     None,
                     Origin::UserAgent,