Bug 1629381 - CanvasRenderingContext2D.drawImage shouldn't throw for e.g <video> if there's no valid surface to draw. r=sotaro

As per spec see comment.

Differential Revision: https://phabricator.services.mozilla.com/D103157

dom/canvas/CanvasRenderingContext2D.cpp

@@ -4518,11 +4518,16 @@ void CanvasRenderingContext2D::DrawImage(const CanvasImageSource& aImage,
     }
 
     if (!res.mSourceSurface && !res.mDrawInfo.mImgContainer) {
-      // The spec says to silently do nothing in the following cases:
+      // https://html.spec.whatwg.org/#check-the-usability-of-the-image-argument:
+      //
+      // Only throw if the request is broken and the element is an
+      // HTMLImageElement / SVGImageElement. Note that even for those the spec
+      // says to silently do nothing in the following cases:
       //   - The element is still loading.
       //   - The image is bad, but it's not in the broken state (i.e., we could
       //     decode the headers and get the size).
-      if (!res.mIsStillLoading && !res.mHasSize) {
+      if (!res.mIsStillLoading && !res.mHasSize &&
+          (aImage.IsHTMLImageElement() || aImage.IsSVGImageElement())) {
         aError.ThrowInvalidStateError("Passed-in image is \"broken\"");
       }
       return;

dom/media/test/test_eme_canvas_blocked.html

@@ -27,13 +27,13 @@ function startTest(test, token)
     canvas.height = video.videoHeight;
     document.body.appendChild(canvas);
     var ctx = canvas.getContext("2d");
-    var threwError = false;
-    try {
-      ctx.drawImage(video, 0, 0);
-    } catch (ex) {
-      threwError = true;
+    ctx.drawImage(video, 0, 0);
+    let pixels = ctx.getImageData(0, 0, canvas.width, canvas.height).data;
+    for (let byte of pixels) {
+      if (byte != 0) {
+        ok(false, "Should not draw EME video to canvas");
+      }
     }
-    ok(threwError, TimeStamp(token) + " - Should throw an error when trying to draw EME video to canvas.");
     p1.resolve();
   });
 

dom/media/test/test_reset_src.html

@@ -33,14 +33,13 @@ function onLoadedData_Audio(e) {
   is(t.mozPaintedFrames, 0, t.name + ": mozPaintedFrames should be zero when there is no video.");
   is(t.mozFrameDelay, 0, t.name + ": mozFrameDelay should be zero when there is no video.");
   var c = document.getElementsByTagName("canvas")[0].getContext("2d");
+  var threw = false;
   try {
     c.drawImage(t, 0, 0, t.videoHeight, t.videoWidth);
   } catch (ex) {
-    ok(true, t.name + ": Trying to draw to a canvas should throw, since we don't have a frame anymore");
-    finish(t);
-    return;
+    threw = true;
   }
-  ok(false, t.name + ": We should not succeed to draw a video frame on the canvas.");
+  ok(!threw, t.name + ": Even though we don't succeed to draw a video frame on the canvas, we shouldn't throw.");
   finish(t);
 }