Correct SourceImageStatus in OffscreenCanvas::getSourceImageForCanvas

third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-empty-image-source.html

+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<script>
+test(function() {
+    var patternCanvas = new OffscreenCanvas(0, 50);
+    var patternCanvasCtx = patternCanvas.getContext("2d");
+    patternCanvasCtx.fillStyle = '#fed';
+    patternCanvasCtx.fillRect(0, 0, 15, 15);
+    var myOCanvas = new OffscreenCanvas(100, 100);
+    var myOCanvasCtx = myOCanvas.getContext("2d");
+    var pattern = myOCanvasCtx.createPattern(patternCanvas, 'repeat');
+    myOCanvasCtx.fillStyle = pattern;
+    myOCanvasCtx.fillRect(0, 0, myOCanvas.width, myOCanvas.height);
+    var imageData = myOCanvasCtx.getImageData(0, 0, 1, 1).data;
+    assert_equals(imageData[0], 0);
+    assert_equals(imageData[1], 0);
+    assert_equals(imageData[2], 0);
+    assert_equals(imageData[3], 0);
+}, "CreatePattern using OffcreenCanvas as image source silently fails when offscreenCanvas has zero size");
+</script>