Add canvas usability checks to drawImage()

components/script/canvas_state.rs

@@ -382,9 +382,19 @@ impl CanvasState {
     ) -> ErrorResult {
         let result = match image {
             CanvasImageSource::HTMLCanvasElement(ref canvas) => {
+                // https://html.spec.whatwg.org/multipage/#check-the-usability-of-the-image-argument
+                if !canvas.is_valid() {
+                    return Err(Error::InvalidState);
+                }
+
                 self.draw_html_canvas_element(&canvas, htmlcanvas, sx, sy, sw, sh, dx, dy, dw, dh)
             },
             CanvasImageSource::OffscreenCanvas(ref canvas) => {
+                // https://html.spec.whatwg.org/multipage/#check-the-usability-of-the-image-argument
+                if !canvas.is_valid() {
+                    return Err(Error::InvalidState);
+                }
+
                 self.draw_offscreen_canvas(&canvas, htmlcanvas, sx, sy, sw, sh, dx, dy, dw, dh)
             },
             CanvasImageSource::HTMLImageElement(ref image) => {

components/script/dom/offscreencanvas.rs

@@ -138,6 +138,10 @@ impl OffscreenCanvas {
         ));
         Some(context)
     }
+
+    pub fn is_valid(&self) -> bool {
+        self.Width() != 0 && self.Height() != 0
+    }
 }
 
 impl OffscreenCanvasMethods for OffscreenCanvas {

tests/wpt/metadata/2dcontext/drawing-images-to-the-canvas/2d.drawImage.zerocanvas.html.ini

@@ -1,5 +0,0 @@
-[2d.drawImage.zerocanvas.html]
-  type: testharness
-  [Canvas test: 2d.drawImage.zerocanvas]
-    expected: FAIL
-

tests/wpt/metadata/offscreen-canvas/drawing-images-to-the-canvas/2d.drawImage.zerocanvas.html.ini

@@ -1,4 +0,0 @@
-[2d.drawImage.zerocanvas.html]
-  [OffscreenCanvas test: 2d.drawImage.zerocanvas]
-    expected: FAIL
-

tests/wpt/metadata/offscreen-canvas/drawing-images-to-the-canvas/2d.drawImage.zerocanvas.worker.js.ini

@@ -1,4 +0,0 @@
-[2d.drawImage.zerocanvas.worker.html]
-  [2d]
-    expected: FAIL
-