Add basic SkBitmap StructTraitsTest.

skia/public/interfaces/test/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 skia.mojom;
 
+import "skia/public/interfaces/bitmap.mojom";
 import "skia/public/interfaces/image_filter.mojom";
 
 // All functions on this interface echo their arguments to test StructTraits
 // serialization and deserialization.
 interface TraitsTestService {
   [Sync]
-  EchoImageFilter(ImageFilter b) => (ImageFilter pass);
+  EchoBitmap(Bitmap b) => (Bitmap pass);
+
+  [Sync]
+  EchoImageFilter(ImageFilter i) => (ImageFilter pass);
 };