Mojo: Simplify typemap usage.

mojo/public/cpp/bindings/tests/struct_with_traits_impl.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_TESTS_STRUCT_WITH_TRAITS_IMPL_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_TESTS_STRUCT_WITH_TRAITS_IMPL_H_
 
 #include <stdint.h>
 
 #include <string>
 
 #include "base/strings/string_piece.h"
-#include "mojo/public/cpp/bindings/struct_traits.h"
 
 namespace mojo {
 namespace test {
 
-// The mojom types are forward-declared to avoid circular dependencies between
-// this and generated headers.
-class StructWithTraits;
-class StructWithTraits_Reader;
-
 // A type which knows how to look like a mojo::test::StructWithTraits mojom type
 // by way of mojo::StructTraits.
 class StructWithTraitsImpl {
  public:
   StructWithTraitsImpl();
   ~StructWithTraitsImpl();
 
   void set_bool(bool value) { bool_ = value; }
   bool get_bool() const { return bool_; }
 
@@ skipping 10 matching lines @@
   bool bool_ = false;
   uint32_t uint32_ = 0;
   uint64_t uint64_ = 0;
   std::string string_;
 };
 
 }  // namespace test
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_TESTS_STRUCT_WITH_TRAITS_IMPL_H_