Auto merge of #17916 - DarkDrek:Use_AntialiasMode_in_CanvasPaintThread_new, r=emilio

Use AntialiasMode in CanvasPaintThread::new

Change suggested in #17661

<!-- Please describe your changes on the following line: -->
I only changed `canvas_paint_thread.rs` since `CanvasPaintThread::start` is used outside of the current crate and `azure::azure_hl::AntialiasMode` isn't available there.

---
<!-- 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 #17661 (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [X] These changes do not require tests because @jdm said so

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- 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/17916)
<!-- Reviewable:end -->

components/canvas/canvas_paint_thread.rs

@@ -80,13 +80,7 @@ struct CanvasPaintState<'a> {
 }
 
 impl<'a> CanvasPaintState<'a> {
-    fn new(antialias: bool) -> CanvasPaintState<'a> {
-        let antialias = if antialias {
-            AntialiasMode::Default
-        } else {
-            AntialiasMode::None
-        };
-
+    fn new(antialias: AntialiasMode) -> CanvasPaintState<'a> {
         CanvasPaintState {
             draw_options: DrawOptions::new(1.0, CompositionOp::Over, antialias),
             fill_style: Pattern::Color(ColorPattern::new(Color::black())),
@@ -104,7 +98,7 @@ impl<'a> CanvasPaintState<'a> {
 impl<'a> CanvasPaintThread<'a> {
     fn new(size: Size2D<i32>,
            webrender_api_sender: webrender_api::RenderApiSender,
-           antialias: bool) -> CanvasPaintThread<'a> {
+           antialias: AntialiasMode) -> CanvasPaintThread<'a> {
         let draw_target = CanvasPaintThread::create(size);
         let path_builder = draw_target.create_path_builder();
         let webrender_api = webrender_api_sender.create_api();
@@ -127,6 +121,11 @@ impl<'a> CanvasPaintThread<'a> {
                  antialias: bool)
                  -> IpcSender<CanvasMsg> {
         let (sender, receiver) = ipc::channel::<CanvasMsg>().unwrap();
+        let antialias = if antialias {
+            AntialiasMode::Default
+        } else {
+            AntialiasMode::None
+        };
         thread::Builder::new().name("CanvasThread".to_owned()).spawn(move || {
             let mut painter = CanvasPaintThread::new(size, webrender_api_sender, antialias);
             loop {
@@ -550,7 +549,7 @@ impl<'a> CanvasPaintThread<'a> {
 
     fn recreate(&mut self, size: Size2D<i32>) {
         self.drawtarget = CanvasPaintThread::create(size);
-        self.state = CanvasPaintState::new(self.state.draw_options.antialias == AntialiasMode::Default);
+        self.state = CanvasPaintState::new(self.state.draw_options.antialias);
         self.saved_states.clear();
         // Webrender doesn't let images change size, so we clear the webrender image key.
         if let Some(image_key) = self.image_key.take() {