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..abd64fc16fd0504990de750418bebe3928794c76
--- /dev/null
+++ b/LayoutTests/http/tests/xmlhttprequest/workers/resources/xmlhttprequest-response-type-blob.js
@@ -0,0 +1,30 @@
+importScripts("../../../resources/js-test-pre.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();
+    }
+}