[GeometryInterface] Implement DOMQuad and DOMQuadInit.

third_party/WebKit/Source/core/dom/DOMQuadInit.idl

Index: third_party/WebKit/Source/core/dom/DOMQuadInit.idl
diff --git a/third_party/WebKit/Source/core/dom/DOMQuadInit.idl b/third_party/WebKit/Source/core/dom/DOMQuadInit.idl
new file mode 100644
index 0000000000000000000000000000000000000000..126a47a9894db4c21a48fd1348d962370f6679fc
--- /dev/null
+++ b/third_party/WebKit/Source/core/dom/DOMQuadInit.idl
@@ -0,0 +1,12 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// https://drafts.fxtf.org/geometry/#dictdef-domquadinit
+
+dictionary DOMQuadInit {
+    DOMPointInit p1;
+    DOMPointInit p2;
+    DOMPointInit p3;
+    DOMPointInit p4;
+};