Support FormData on WorkerGlobalScope.

LayoutTests/fast/workers/resources/worker-formdata.js

Index: LayoutTests/fast/workers/resources/worker-formdata.js
diff --git a/LayoutTests/fast/workers/resources/worker-formdata.js b/LayoutTests/fast/workers/resources/worker-formdata.js
new file mode 100644
index 0000000000000000000000000000000000000000..b0c1a51e6dbc1cfef0d0098a98c053495b22e2aa
--- /dev/null
+++ b/LayoutTests/fast/workers/resources/worker-formdata.js
@@ -0,0 +1,19 @@
+importScripts('../../../resources/js-test.js');
+
+description("Test FormData interface object");
+
+shouldBeDefined("FormData");
+shouldBe("FormData.length", "0");
+
+var formData = new FormData();
+
+shouldBeNonNull("formData");
+
+shouldBeTrue("FormData.prototype.hasOwnProperty('append')");
+shouldNotThrow("formData.append('key', 'value');");
+var blob = new Blob([]);
+shouldBeNonNull("blob");
+shouldNotThrow("formData.append('key', blob);");
+shouldNotThrow("formData.append('key', blob, 'filename');");
+shouldThrow("postMessage(formData)");
+finishJSTest();