canvas: Add OffscreenCanvas 'transferToImageBitmap' method (#37880)

Follow the HTML speficication and add missing 'transferToImageBitmap'
method to OffscreenCanvas interface.

https://html.spec.whatwg.org/multipage/#dom-offscreencanvas-transfertoimagebitmap

Testing: Improvements in the following tests
- html/canvas/offscreen/compositing/2d.composite.grid*
- html/canvas/offscreen/fill-and-stroke-styles/2d.gradient*
- html/canvas/offscreen/manual/the-offscreen-canvas/offscreencanvas*
- html/canvas/offscreen/reset/2d.reset*
- html/canvas/offscreen/text/2d.text*

Fixes (partially): #34111

Signed-off-by: Andrei Volykhin <andrei.volykhin@gmail.com>

components/script/canvas_state.rs

@@ -292,6 +292,14 @@ impl CanvasState {
         *self.state.borrow_mut() = CanvasContextState::new();
     }
 
+    pub(crate) fn reset_bitmap(&self) {
+        if !self.is_paintable() {
+            return;
+        }
+
+        self.send_canvas_2d_msg(Canvas2dMsg::ClearRect(self.size.get().to_f32().into()));
+    }
+
     fn create_drawable_rect(&self, x: f64, y: f64, w: f64, h: f64) -> Option<Rect<f32>> {
         if !([x, y, w, h].iter().all(|val| val.is_finite())) {
             return None;