Add SurfaceReference class.

cc/ipc/struct_traits_unittest.cc

Index: cc/ipc/struct_traits_unittest.cc
diff --git a/cc/ipc/struct_traits_unittest.cc b/cc/ipc/struct_traits_unittest.cc
index a952b11a048c317348e4725121636fddc5dc9c26..b7fa58858add45f0a7f3f6ec0682069e77dfc36d 100644
--- a/cc/ipc/struct_traits_unittest.cc
+++ b/cc/ipc/struct_traits_unittest.cc
@@ -95,6 +95,12 @@ class StructTraitsTest : public testing::Test, public mojom::TraitsTestService {
     callback.Run(s);
   }
 
+  void EchoSurfaceReference(
+      const SurfaceReference& s,
+      const EchoSurfaceReferenceCallback& callback) override {
+    callback.Run(s);
+  }
+
   void EchoSurfaceSequence(
       const SurfaceSequence& s,
       const EchoSurfaceSequenceCallback& callback) override {
@@ -779,6 +785,22 @@ TEST_F(StructTraitsTest, SurfaceId) {
   EXPECT_EQ(local_frame_id, output.local_frame_id());
 }
 
+TEST_F(StructTraitsTest, SurfaceReference) {
+  const SurfaceId parent_id(
+      FrameSinkId(2016, 1234),
+      LocalFrameId(0xfbadbeef, base::UnguessableToken::Deserialize(123, 456)));
+  const SurfaceId child_id(
+      FrameSinkId(1111, 9999),
+      LocalFrameId(0xabcdabcd, base::UnguessableToken::Deserialize(333, 333)));
+  const SurfaceReference input(parent_id, child_id);
+
+  mojom::TraitsTestServicePtr proxy = GetTraitsTestProxy();
+  SurfaceReference output;
+  proxy->EchoSurfaceReference(input, &output);
+  EXPECT_EQ(parent_id, output.parent_id());
+  EXPECT_EQ(child_id, output.child_id());
+}
+
 TEST_F(StructTraitsTest, SurfaceSequence) {
   const FrameSinkId frame_sink_id(2016, 1234);
   const uint32_t sequence = 0xfbadbeef;