Implement cc::SharedQuadState StructTraits

cc/ipc/traits_test_service.mojom

Index: cc/ipc/traits_test_service.mojom
diff --git a/cc/ipc/traits_test_service.mojom b/cc/ipc/traits_test_service.mojom
index 71958b1c4dd1925a98065b2fd004f630199f29c0..d09e8eb155e864ead16a9adb4512856d92ff2b89 100644
--- a/cc/ipc/traits_test_service.mojom
+++ b/cc/ipc/traits_test_service.mojom
@@ -7,13 +7,16 @@ module cc.mojom;
 import "cc/ipc/begin_frame_args.mojom";
 import "cc/ipc/render_pass_id.mojom";
 import "cc/ipc/returned_resource.mojom";
+import "cc/ipc/shared_quad_state.mojom";
 import "cc/ipc/surface_id.mojom";
 import "cc/ipc/transferable_resource.mojom";
 
 interface TraitsTestService {
   EchoBeginFrameArgs(BeginFrameArgs b) => (BeginFrameArgs pass);
   EchoRenderPassId(RenderPassId r) => (RenderPassId pass);
-  EchoReturnedResource(ReturnedResource r) => (ReturnedResource r);
+  EchoReturnedResource(ReturnedResource r) => (ReturnedResource pass);
+  [Sync]
+  EchoSharedQuadState(SharedQuadState s) => (SharedQuadState pass);
   EchoSurfaceId(SurfaceId s) => (SurfaceId pass);
   EchoTransferableResource(TransferableResource t) =>
       (TransferableResource pass);