chromium/third_party/blink/web_tests/compositing/layer-creation/spanOverlapsCanvas.html

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
	<meta name="viewport" content="width=480"/>

	<script>
      if (window.internals)
          internals.runtimeFlags.accelerated2dCanvasEnabled = true;

	    function init() {
	        var ctx = document.getElementById("world").getContext("2d");
	        ctx.fillStyle = "red";
	        ctx.fillRect(0,0,ctx.canvas.width,ctx.canvas.height);
	        
            if (window.testRunner) {
                testRunner.dumpAsTextWithPixelResults();
                testRunner.setCustomTextOutput(internals.layerTreeAsText(document));
            }
	    }
	</script>

	<style>
        #output
        {
            width: 100px;
            height: 50px;
            background-color: green;
            position: absolute;
        }
	</style>
</head>
<body onLoad="init()">
	<div id="output"></div>
	<canvas id="world" width="100" height="50"></canvas>
</body>
</html>