Auto merge of #14089 - Wafflespeanut:tocss, r=SimonSapin

Make use of Servo-specific ToCss everywhere!

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

This will allow types to be generic over our local `ToCss`

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [ ] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors

<!-- Either: -->
- [x] These changes do not require tests because it's a refactor

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/14089)
<!-- Reviewable:end -->

components/script/dom/cssstyledeclaration.rs

@@ -2,7 +2,6 @@
  * 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::ToCss;
 use dom::bindings::codegen::Bindings::CSSStyleDeclarationBinding::{self, CSSStyleDeclarationMethods};
 use dom::bindings::error::{Error, ErrorResult, Fallible};
 use dom::bindings::inheritance::Castable;
@@ -20,6 +19,7 @@ use style::parser::ParserContextExtraData;
 use style::properties::{Shorthand, Importance, PropertyDeclarationBlock};
 use style::properties::{is_supported_property, parse_one_declaration, parse_style_attribute};
 use style::selector_impl::PseudoElement;
+use style_traits::ToCss;
 
 // http://dev.w3.org/csswg/cssom/#the-cssstyledeclaration-interface
 #[dom_struct]

components/script/dom/mediaquerylist.rs

@@ -2,7 +2,6 @@
  * 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::ToCss;
 use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::EventHandlerBinding::EventHandlerNonNull;
 use dom::bindings::codegen::Bindings::EventListenerBinding::EventListener;
@@ -22,7 +21,7 @@ use std::cell::Cell;
 use std::rc::Rc;
 use style;
 use style::media_queries::{Device, MediaType};
-use style_traits::{PagePx, ViewportPx};
+use style_traits::{PagePx, ToCss, ViewportPx};
 
 pub enum MediaQueryListMatchState {
     Same(bool),