[GeometryInterface] Add Constructor() at DOMMatrixReadOnly.

third_party/WebKit/LayoutTests/fast/dom/geometry-interfaces-dom-matrix-readonly.html

Index: third_party/WebKit/LayoutTests/fast/dom/geometry-interfaces-dom-matrix-readonly.html
diff --git a/third_party/WebKit/LayoutTests/fast/dom/geometry-interfaces-dom-matrix-readonly.html b/third_party/WebKit/LayoutTests/fast/dom/geometry-interfaces-dom-matrix-readonly.html
index 0019e14e50103dc6b8bf3ef7a2ad98b883eacd5c..49f861b47afe345396103c7c160ee9bb66abb561 100644
--- a/third_party/WebKit/LayoutTests/fast/dom/geometry-interfaces-dom-matrix-readonly.html
+++ b/third_party/WebKit/LayoutTests/fast/dom/geometry-interfaces-dom-matrix-readonly.html
@@ -3,6 +3,12 @@
 <script src="../../resources/testharnessreport.js"></script>
 <script src="./resources/geometry-interfaces-test-helpers.js"></script>
 <script>
+
+test(() => {
+  var matrix = new DOMMatrixReadOnly();
+  assert_identity_2d_matrix(matrix);
+}, "DOMMatrixReadOnly constructor");
+
 test(() => {
   var matrix2d = new DOMMatrixReadOnly([1, 2, 3, 3.1, 2, 1]);
   assert_2d_matrix_equals(matrix2d, [1, 2, 3, 3.1, 2, 1]);