Conformance issue, should not fail creation of of canvas larger than maximum possible

Conformance test Canvas3D_conformance_drawingbuffer_test::test_drawingbuffer_test_2() fails, as canvas doesn't fulfill the WebGL spec 2.2: "If the requested width or height cannot be satisfied, either when the drawing buffer is first created or when the width and height attributes of the HTMLCanvasElement are changed, a drawing buffer with smaller dimensions shall be created. "