Incorrect is_rect_valid checks in CanvasRenderingContext2D::drawImage.

[Ms2ger]

Blocks #10597.

Nothing in the spec seems to support throwing IndexSizeErrors with empty rectangles. The spec may have changed since we implemented it, though.

Unfortunately, there seem to be some tests that will start failing with this change (web-platform-tests/wpt#2835). We probably need to write some more tests too.

• Spec: https://html.spec.whatwg.org/multipage/#dom-context-2d-drawimage.
• Code: components/script/dom/canvasrenderingcontext2d.rs.
• Test: at least 2dcontext/conformance-requirements/2d.voidreturn.html.

[n0max]

Hi, I like to work on this.

The tests
/2dcontext/conformance-requirements/2d.voidreturn.html
/2dcontext/drawing-images-to-the-canvas/2d.drawImage.zerosource.html
are expected to fail and with the changes they pass.

What additional tests are required?

[jdm]

Running ./mach test-wpt tests/wpt/web-platform-tests/2dcontext should not show any unexpected failures (only passes) with these changes.

[n0max]

I meant both tests are already changed for the current spec and set to FAIL in https://github.com/servo/servo/blob/17fe437fb72694763f0f7f1b4701127ebc2ef5aa/tests/wpt/metadata/2dcontext/drawing-images-to-the-canvas/2d.drawImage.zerosource.html.ini
and https://github.com/servo/servo/blob/234951e4b6d66891cd0cc9705f42e3ca16d9e3d5/tests/wpt/metadata/2dcontext/conformance-requirements/2d.voidreturn.html.ini

Running ./mach test-wpt tests/wpt/web-platform-tests/2dcontext shows

  ▶ Unexpected subtest result in /2dcontext/conformance-requirements/2d.voidreturn.html:
  └ PASS [expected FAIL] void methods return undefined

  ▶ Unexpected subtest result in /2dcontext/drawing-images-to-the-canvas/2d.drawImage.zerosource.html:
  └ PASS [expected FAIL] drawImage with zero-sized source rectangle draws nothing without exception

When I change the ini files to PASS the test runs without failures.