Auto merge of #15357 - dashed:gh-15207, r=Wafflespeanut,emilio

Refactor outline-style to accept "auto" value in addition to border-style values.

Fixes https://github.com/servo/servo/issues/15207

Refactored as per https://github.com/servo/servo/issues/15207#issuecomment-275171590 .

<!-- Please describe your changes on the following line: -->

- [x] Correct refactor? I'd appreciate any feedback on this.
- [x] ~~~proper borderstyle value for `outline-style: auto;`?~~~ ~~~(EDIT: deferred to a `FIXME`)~~~ (EDIT2: it is now solid for behaviour parity with firefox)
- [x] squash pending PR review
- [x] mako code review

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #15207 (github issue number if applicable).

<!-- Either: -->
- [x] There are tests for these changes

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tests/unit/style/parsing/border.rs

@@ -5,11 +5,12 @@
 use cssparser::Parser;
 use media_queries::CSSErrorReporterTest;
 use servo_url::ServoUrl;
-use style::parser::ParserContext;
+use style::parser::{ParserContext, Parse};
 use style::properties::longhands::{border_image_outset, border_image_repeat, border_image_slice};
 use style::properties::longhands::{border_image_source, border_image_width};
 use style::properties::shorthands::border_image;
 use style::stylesheets::Origin;
+use style_traits::ToCss;
 
 #[test]
 fn border_image_shorthand_should_parse_when_all_properties_specified() {
@@ -122,3 +123,19 @@ fn border_image_outset_should_return_length_on_length_zero() {
     let result = border_image_outset::parse(&context, &mut parser);
     assert_eq!(result.unwrap(), parse_longhand!(border_image_outset, "0em"));
 }
+
+#[test]
+fn test_border_style() {
+    use style::values::specified::BorderStyle;
+
+    assert_roundtrip_with_context!(BorderStyle::parse, r#"none"#);
+    assert_roundtrip_with_context!(BorderStyle::parse, r#"hidden"#);
+    assert_roundtrip_with_context!(BorderStyle::parse, r#"solid"#);
+    assert_roundtrip_with_context!(BorderStyle::parse, r#"double"#);
+    assert_roundtrip_with_context!(BorderStyle::parse, r#"dotted"#);
+    assert_roundtrip_with_context!(BorderStyle::parse, r#"dashed"#);
+    assert_roundtrip_with_context!(BorderStyle::parse, r#"groove"#);
+    assert_roundtrip_with_context!(BorderStyle::parse, r#"ridge"#);
+    assert_roundtrip_with_context!(BorderStyle::parse, r#"inset"#);
+    assert_roundtrip_with_context!(BorderStyle::parse, r#"outset"#);
+}

tests/unit/style/parsing/mod.rs

@@ -75,6 +75,7 @@ mod image;
 mod inherited_box;
 mod inherited_text;
 mod mask;
+mod outline;
 mod position;
 mod selectors;
 mod supports;

tests/unit/style/parsing/outline.rs

@@ -0,0 +1,37 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+use cssparser::Parser;
+use media_queries::CSSErrorReporterTest;
+use style::parser::ParserContext;
+use style::stylesheets::Origin;
+use style_traits::ToCss;
+
+#[test]
+fn test_outline_style() {
+    use style::properties::longhands::outline_style;
+
+    assert_roundtrip_with_context!(outline_style::parse, r#"auto"#);
+    assert_roundtrip_with_context!(outline_style::parse, r#"none"#);
+    assert_roundtrip_with_context!(outline_style::parse, r#"solid"#);
+    assert_roundtrip_with_context!(outline_style::parse, r#"double"#);
+    assert_roundtrip_with_context!(outline_style::parse, r#"dotted"#);
+    assert_roundtrip_with_context!(outline_style::parse, r#"dashed"#);
+    assert_roundtrip_with_context!(outline_style::parse, r#"groove"#);
+    assert_roundtrip_with_context!(outline_style::parse, r#"ridge"#);
+    assert_roundtrip_with_context!(outline_style::parse, r#"inset"#);
+    assert_roundtrip_with_context!(outline_style::parse, r#"outset"#);
+
+    {
+        // The outline-style property accepts the same values as border-style,
+        // except that 'hidden' is not a legal outline style.
+
+        let url = ::servo_url::ServoUrl::parse("http://localhost").unwrap();
+        let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+        let mut parser = Parser::new(r#"hidden"#);
+        let parsed = outline_style::parse(&context, &mut parser);
+        assert!(parsed.is_err());
+    };
+
+}