Implement URLSearchParams.

LayoutTests/fast/domurl/resources/testharness-extras.js

Index: LayoutTests/fast/domurl/resources/testharness-extras.js
diff --git a/LayoutTests/fast/domurl/resources/testharness-extras.js b/LayoutTests/fast/domurl/resources/testharness-extras.js
new file mode 100644
index 0000000000000000000000000000000000000000..5b7661b79315d930c81437978b44817617da295e
--- /dev/null
+++ b/LayoutTests/fast/domurl/resources/testharness-extras.js
@@ -0,0 +1,25 @@
+/*
+Extending the W3C testharness.js with locally useful functionality.
+*/
+
+// 'Untyped' checking of exception messages; for when you want
+// to test the error message returned rather than the exact kind.
+function assert_throws_message(func, expected, name) {
+    try {
+        func();
+    } catch (ex) {
+        assert_equals(String(ex), expected);
+        if (name)
+            assert_equals(ex.name, name);
+        return;
+    }
+    assert_true(false, 'Expected an exception with string: ' + expected);
+}
+
+function assert_type_error(f, msg) {
+    assert_throws(TypeError(), f, msg);
+}
+
+function assert_syntax_error(f, msg) {
+    assert_throws(SyntaxError(), f, msg);
+}