Struct traits for gfx::Range and gfx::RangeF.

ui/gfx/range/mojo/range_traits_test_service.mojom

+// Copyright 2016 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.
+
+module gfx.mojom;
+
+import "ui/gfx/range/mojo/range.mojom";
+
+// All functions on this interface echo their arguments to test StructTraits
+// serialization and deserialization.
+interface RangeTraitsTestService {
+  [Sync]
+  EchoRange(Range p) => (Range pass);
+
+  [Sync]
+  EchoRangeF(RangeF p) => (RangeF pass);
+};