Don't use utf8 logic to parse unquoted urls.

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "cssparser"
-version = "0.7.0"
+version = "0.7.1"
 authors = [ "Simon Sapin <simon.sapin@exyr.org>" ]
 
 description = "Rust implementation of CSS Syntax Level 3"
@@ -25,3 +25,4 @@ serde = {version = ">=0.6.6, <0.9", optional = true}
 [features]
 serde-serialization = [ "serde" ]
 heap_size = [ "heapsize" ]
+bench = []

src/lib.rs

@@ -5,6 +5,7 @@
 #![crate_name = "cssparser"]
 #![crate_type = "rlib"]
 
+#![cfg_attr(feature = "bench", feature(test))]
 #![deny(missing_docs)]
 
 /*!

src/tests.rs

@@ -2,6 +2,9 @@
  * 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/. */
 
+#[cfg(feature = "bench")]
+extern crate test;
+
 use std::borrow::Cow::{self, Borrowed};
 use std::fs::File;
 use std::io::{self, Write};
@@ -10,6 +13,9 @@ use std::process::Command;
 use rustc_serialize::json::{self, Json, ToJson};
 use tempdir::TempDir;
 
+#[cfg(feature = "bench")]
+use self::test::Bencher;
+
 use encoding::label::encoding_from_whatwg_label;
 
 use super::{Parser, Delimiter, Token, NumericValue, PercentageValue, SourceLocation,
@@ -576,6 +582,24 @@ impl ToJson for Color {
     }
 }
 
+#[cfg(feature = "bench")]
+const BACKGROUND_IMAGE: &'static str = include_str!("big-data-url.css");
+
+#[cfg(feature = "bench")]
+#[bench]
+fn unquoted_url(b: &mut Bencher) {
+    b.iter(|| {
+        let mut input = Parser::new(BACKGROUND_IMAGE);
+        input.look_for_var_functions();
+
+        let result = input.try(|input| input.expect_url());
+
+        assert!(result.is_ok());
+
+        input.seen_var_functions();
+        (result.is_ok(), input.seen_var_functions())
+    })
+}
 
 struct JsonParser;
 
@@ -667,7 +691,6 @@ fn component_values_to_json(input: &mut Parser) -> Vec<Json> {
     values
 }
 
-
 fn one_component_value_to_json(token: Token, input: &mut Parser) -> Json {
     fn numeric(value: NumericValue) -> Vec<json::Json> {
         vec![