Add basic SkBitmap StructTraitsTest.

skia/public/interfaces/test/traits_test_service.mojom

Index: skia/public/interfaces/test/traits_test_service.mojom
diff --git a/skia/public/interfaces/test/traits_test_service.mojom b/skia/public/interfaces/test/traits_test_service.mojom
index fc1d2be41eaab8d9c9c158755322873a71a3e94b..eaa829e8163329b4d5759510b75d83dfb25e2dfe 100644
--- a/skia/public/interfaces/test/traits_test_service.mojom
+++ b/skia/public/interfaces/test/traits_test_service.mojom
@@ -4,11 +4,15 @@
 
 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);
 };