Make callback arg non-nullable on canvas.toBlob

third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-toBlob-invalid.js

Index: third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-toBlob-invalid.js
diff --git a/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-toBlob-invalid.js b/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-toBlob-invalid.js
new file mode 100644
index 0000000000000000000000000000000000000000..8d1e8ec3a05f08af74748f97281a1390623774b9
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-toBlob-invalid.js
@@ -0,0 +1,17 @@
+description("Test the handling of invalid arguments in canvas toBlob().");
+
+var canvas = document.createElement('canvas');
+var ctx = canvas.getContext("2d"); 
+ctx.strokeStyle = "red";
+ctx.strokeRect(0, 0, 50, 50);
+
+shouldThrow("canvas.toBlob();");
+shouldThrow("canvas.toBlob(null);");
+shouldThrow("canvas.toBlob(undefined);");
+// Passing the callback argument without blob handle silently fails.
+shouldNotThrow("canvas.toBlob(function() {});");
+
+// Invalid quality argument will fall back to default value
+shouldNotThrow("canvas.toBlob(function(blob) {}, 'image/jpeg', 500)");
+
+