Make OffscreenCanvas a member of CanvasImageSource

third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-2d-drawImage-expected.html

Index: third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-2d-drawImage-expected.html
diff --git a/third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-2d-drawImage-expected.html b/third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-2d-drawImage-expected.html
index 89e26a06369ee074fca1a55544e1fa11cfb691e6..c09dbc71b4025e5e29b4e56caa43819a6503bbd6 100644
--- a/third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-2d-drawImage-expected.html
+++ b/third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-2d-drawImage-expected.html
@@ -13,6 +13,8 @@
 <canvas id="videoOutput" width="150" height="150"></canvas>
 <canvas id="imageOutput" width="150" height="150"></canvas>
 <canvas id="canvasOutput" width="150" height="150"></canvas>
+<canvas id="offscreenCanvas2DOutput" width="150" height="150"></canvas>
+<canvas id="offscreenCanvasWebGLOutput" width="150" height="150"></canvas>
 
 <script>
 function drawImageSourceToHTMLCanvas(imageSource, outputCanvas) { 
@@ -55,6 +57,17 @@ htmlCanvasCtx.fillStyle = "red";
 htmlCanvasCtx.fillRect(15, 0, 30, 30);
 drawImageSourceToHTMLCanvas(htmlCanvas, document.getElementById('canvasOutput'));
 
+// Assume html and offscreen canvases should yield identical results
+drawImageSourceToHTMLCanvas(htmlCanvas, document.getElementById('offscreenCanvas2DOutput'));
+
+// Image source as OffscreenCanvas with webGL context
+var glCanvas = document.createElement('canvas');
+glCanvas.width = glCanvas.height = 30;
+var gl = glCanvas.getContext("webgl");
+gl.clearColor(0.0, 0.0, 1.0, 1.0);
+gl.clear(gl.COLOR_BUFFER_BIT);
+drawImageSourceToHTMLCanvas(glCanvas, document.getElementById('offscreenCanvasWebGLOutput'));
+
 </script>
 </body>