Implement Asynchronous image encoding for Canvas.toBlob

LayoutTests/fast/canvas/canvas-toBlob-toDataURL-race-imageEncoder-jpeg-expected.txt

Index: LayoutTests/fast/canvas/canvas-toBlob-toDataURL-race-imageEncoder-jpeg-expected.txt
diff --git a/LayoutTests/fast/canvas/canvas-toBlob-toDataURL-race-imageEncoder-jpeg-expected.txt b/LayoutTests/fast/canvas/canvas-toBlob-toDataURL-race-imageEncoder-jpeg-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..1c2cee5513baf7eaac6601cae2b4486b9335aea0
--- /dev/null
+++ b/LayoutTests/fast/canvas/canvas-toBlob-toDataURL-race-imageEncoder-jpeg-expected.txt
@@ -0,0 +1,21 @@
+Verifies if JPEG image encoding on main thread (toDataURL) conflicts with image encoding on async thread (toBlob)
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS successfullyParsed is true
+
+TEST COMPLETE
+PASS canvasCtxs[0].getImageData(0, 0, 2500, 1750).data[25] is non-zero.
+PASS canvasCtxs[0].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[1].getImageData(0, 0, 2500, 1750).data[25]
+PASS canvasCtxs[1].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[2].getImageData(0, 0, 2500, 1750).data[25]
+PASS canvasCtxs[2].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[3].getImageData(0, 0, 2500, 1750).data[25]
+PASS canvasCtxs[3].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[4].getImageData(0, 0, 2500, 1750).data[25]
+PASS canvasCtxs[4].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[5].getImageData(0, 0, 2500, 1750).data[25]
+PASS canvasCtxs[5].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[6].getImageData(0, 0, 2500, 1750).data[25]
+PASS canvasCtxs[6].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[7].getImageData(0, 0, 2500, 1750).data[25]
+PASS canvasCtxs[7].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[8].getImageData(0, 0, 2500, 1750).data[25]
+PASS canvasCtxs[8].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[9].getImageData(0, 0, 2500, 1750).data[25]
+PASS canvasCtxs[9].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[10].getImageData(0, 0, 2500, 1750).data[25]
+PASS canvasCtxs[10].getImageData(0, 0, 2500, 1750).data[25] is canvasCtxs[11].getImageData(0, 0, 2500, 1750).data[25]
+