Use downloadToFile option when XHR downloads a Blob

LayoutTests/http/tests/xmlhttprequest/workers/resources/xmlhttprequest-response-type-blob.js

Index: LayoutTests/http/tests/xmlhttprequest/workers/resources/xmlhttprequest-response-type-blob.js
diff --git a/LayoutTests/http/tests/xmlhttprequest/workers/resources/xmlhttprequest-response-type-blob.js b/LayoutTests/http/tests/xmlhttprequest/workers/resources/xmlhttprequest-response-type-blob.js
new file mode 100644
index 0000000000000000000000000000000000000000..6328444225450d5e82fec45fe461c43b6b0f3e99
--- /dev/null
+++ b/LayoutTests/http/tests/xmlhttprequest/workers/resources/xmlhttprequest-response-type-blob.js
@@ -0,0 +1,30 @@
+importScripts("/js-test-resources/js-test.js");
+importScripts("worker-pre.js");
+
+function init() {
+    var global = self;
+
+    try {
+        global.req = new XMLHttpRequest;
+        req.responseType = "blob";
+        req.open("GET", "../../resources/get.txt", true);
+        req.onreadystatechange = function() {
+            if (req.readyState == 4) {
+                shouldBe("req.status", "200");
+                shouldBe("req.response.size", "4");
+                var reader = new FileReader();
+                reader.onload = function (evt) {
+                    global.buffer = evt.target.result;
+                    shouldBeEqualToString("buffer", "PASS");
+                    testPassed("XHR with responseType=\"blob\" succeeded");
+                    finishJSTest();
+                };
+                reader.readAsText(req.response, "utf-8");
+            }
+        };
+        req.send(null);
+    } catch (e) {
+        testFailed("failed to create XMLHttpRequest with exception: " + e.message);
+        finishJSTest();
+    }
+}