script: Reduce the use of `unsafe` in LayoutDom (#31979)

Remove the use of unsafe code in the layout wrappers of the DOM. The
main change here is that `unsafe_get()` no longer needs to be an unsafe
method, which allows us to transitively remove or reduce unsafe blocks
from callers. The function itself is not renamed, because it's still
a bit dangerous to start removing the layers of abstraction from actual
DOM nodes.

In addition `init_style_and_opaque_layout_data` can be merged into
`initialize_data`, which removes one more unsafe method.

Finally, a "Safety" section is added to some unsafe methods.

1 files changed, 3 insertions, 6 deletions

diff --git a/components/script/dom/canvasrenderingcontext2d.rs b/components/script/dom/canvasrenderingcontext2d.rs
index a12cc5e8e3a..1f4c8bd7152 100644
--- a/components/script/dom/canvasrenderingcontext2d.rs
+++ b/components/script/dom/canvasrenderingcontext2d.rs
@@ -127,23 +127,20 @@ impl CanvasRenderingContext2D {
 }
 
 pub trait LayoutCanvasRenderingContext2DHelpers {
-    #[allow(unsafe_code)]
-    unsafe fn get_ipc_renderer(self) -> IpcSender<CanvasMsg>;
+    fn get_ipc_renderer(self) -> IpcSender<CanvasMsg>;
     fn get_canvas_id(self) -> CanvasId;
 }
 
 impl LayoutCanvasRenderingContext2DHelpers for LayoutDom<'_, CanvasRenderingContext2D> {
-    #[allow(unsafe_code)]
-    unsafe fn get_ipc_renderer(self) -> IpcSender<CanvasMsg> {
+    fn get_ipc_renderer(self) -> IpcSender<CanvasMsg> {
         (self.unsafe_get()).canvas_state.get_ipc_renderer().clone()
     }
 
-    #[allow(unsafe_code)]
     fn get_canvas_id(self) -> CanvasId {
         // FIXME(nox): This relies on the fact that CanvasState::get_canvas_id
         // does nothing fancy but it would be easier to trust a
         // LayoutDom<_>-like type that would wrap the &CanvasState.
-        unsafe { self.unsafe_get().canvas_state.get_canvas_id() }
+        self.unsafe_get().canvas_state.get_canvas_id()
     }
 }