Add SurfaceSequence mojom file to cc/ipc and edit corresponding GYP file

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 0182f694135327c959c2367bcd2ffa426d2de4e0..40919b0bdfd517d4e02a09759c285257d4d5abf7 100644
--- a/cc/ipc/struct_traits_unittest.cc
+++ b/cc/ipc/struct_traits_unittest.cc
@@ -50,6 +50,12 @@ class StructTraitsTest : public testing::Test, public mojom::TraitsTestService {
     callback.Run(s);
   }
 
+  void EchoSurfaceSequence(
+      const SurfaceSequence& s,
+      const EchoSurfaceSequenceCallback& callback) override {
+    callback.Run(s);
+  }
+
   void EchoTransferableResource(
       const TransferableResource& t,
       const EchoTransferableResourceCallback& callback) override {
@@ -134,6 +140,17 @@ TEST_F(StructTraitsTest, SurfaceId) {
   EXPECT_EQ(nonce, output.nonce());
 }
 
+TEST_F(StructTraitsTest, SurfaceSequence) {
+  const uint32_t id_namespace = 2016;
+  const uint32_t sequence = 0xfbadbeef;
+  SurfaceSequence input(id_namespace, sequence);
+  mojom::TraitsTestServicePtr proxy = GetTraitsTestProxy();
+  SurfaceSequence output;
+  proxy->EchoSurfaceSequence(input, &output);
+  EXPECT_EQ(id_namespace, output.id_namespace);
+  EXPECT_EQ(sequence, output.sequence);
+}
+
 TEST_F(StructTraitsTest, SharedQuadState) {
   const gfx::Transform quad_to_target_transform(1.f, 2.f, 3.f, 4.f, 5.f, 6.f,
                                                 7.f, 8.f, 9.f, 10.f, 11.f, 12.f,