Add DOMString floating point string test and fix

Fixes an issue where DOMString::is_valid_floating_point_number_string
was returning true for strings that began with whitespace characters-
TAB, LF, FF, or CR. Also added a unit test to cover this since the
corresponding web-platform-tests are incomplete.

tests/unit/script/domstring.rs

@@ -0,0 +1,20 @@
+// Copyright 2013 The Servo Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use script::test::DOMString;
+
+#[test]
+fn test_domstring_is_valid_floating_point_number_string_leading_whitespace() {
+    assert!(!DOMString::from("\t1").is_valid_floating_point_number_string());
+    assert!(!DOMString::from("\n1").is_valid_floating_point_number_string());
+    // \x0C - form feed
+    assert!(!DOMString::from("\x0C1").is_valid_floating_point_number_string());
+    assert!(!DOMString::from("\r1").is_valid_floating_point_number_string());
+    assert!(!DOMString::from(" 1").is_valid_floating_point_number_string());
+}

tests/unit/script/lib.rs

@@ -2,6 +2,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+#[cfg(test)]
+mod domstring;
 #[cfg(test)]
 mod headers;
 #[cfg(test)]