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, 2 insertions, 2 deletions

diff --git a/components/script/dom/webgl2renderingcontext.rs b/components/script/dom/webgl2renderingcontext.rs
index 351acca1bca..66d2026b8f3 100644
--- a/components/script/dom/webgl2renderingcontext.rs
+++ b/components/script/dom/webgl2renderingcontext.rs
@@ -4474,8 +4474,8 @@ impl WebGL2RenderingContextMethods for WebGL2RenderingContext {
 
 impl LayoutCanvasRenderingContextHelpers for LayoutDom<'_, WebGL2RenderingContext> {
     #[allow(unsafe_code)]
-    unsafe fn canvas_data_source(self) -> HTMLCanvasDataSource {
+    fn canvas_data_source(self) -> HTMLCanvasDataSource {
         let this = self.unsafe_get();
-        (*this.base.to_layout().unsafe_get()).layout_handle()
+        unsafe { (*this.base.to_layout().unsafe_get()).layout_handle() }
     }
 }