Generate a templated Clone method for all mojo structs.

mojo/public/cpp/bindings/tests/struct_traits_unittest.cc

Index: mojo/public/cpp/bindings/tests/struct_traits_unittest.cc
diff --git a/mojo/public/cpp/bindings/tests/struct_traits_unittest.cc b/mojo/public/cpp/bindings/tests/struct_traits_unittest.cc
index 38fbaf11cfbd04fd4ac5d4744dcc0e3fd8893535..e0d4736a686bcc27cf774dff0e0bc39cf531a74e 100644
--- a/mojo/public/cpp/bindings/tests/struct_traits_unittest.cc
+++ b/mojo/public/cpp/bindings/tests/struct_traits_unittest.cc
@@ -242,6 +242,16 @@ TEST_F(StructTraitsTest, EchoStructWithTraits) {
   loop.Run();
 }
 
+TEST_F(StructTraitsTest, CloneStructWithTraitsContainer) {
+  StructWithTraitsContainerPtr container = StructWithTraitsContainer::New();
+  container->f_struct.set_uint32(7);
+  container->f_struct.set_uint64(42);
+  StructWithTraitsContainerPtr cloned_container = container.Clone();
+  EXPECT_EQ(7u, cloned_container->f_struct.get_uint32());
+  EXPECT_EQ(42u, cloned_container->f_struct.get_uint64());
+
+}
+
 TEST_F(StructTraitsTest, EchoPassByValueStructWithTraits) {
   MessagePipe mp;
   PassByValueStructWithTraitsImpl input;