Mojo C++ bindings: add a new mode to generator to use native STL/WTF types

mojo/public/cpp/bindings/lib/bindings_internal.h

Index: mojo/public/cpp/bindings/lib/bindings_internal.h
diff --git a/mojo/public/cpp/bindings/lib/bindings_internal.h b/mojo/public/cpp/bindings/lib/bindings_internal.h
index b32cf694b9e62ed5b47d8e4c382643b74f108eec..b37d87273f7b7aab715177084a3962731300250c 100644
--- a/mojo/public/cpp/bindings/lib/bindings_internal.h
+++ b/mojo/public/cpp/bindings/lib/bindings_internal.h
@@ -7,6 +7,9 @@
 
 #include <stdint.h>
 
+#include <functional>
+
+#include "base/template_util.h"
 #include "mojo/public/cpp/bindings/interface_id.h"
 #include "mojo/public/cpp/bindings/lib/template_util.h"
 #include "mojo/public/cpp/system/core.h"
@@ -315,6 +318,16 @@ struct BelongsTo {
       static_cast<uint32_t>(MojomTypeTraits<T>::category & categories) != 0;
 };
 
+template <typename T>
+struct EnumHashImpl {
+  static_assert(std::is_enum<T>::value, "Incorrect hash function.");
+
+  size_t operator()(T input) const {
+    using UnderlyingType = typename base::underlying_type<T>::type;
+    return std::hash<UnderlyingType>()(static_cast<UnderlyingType>(input));
+  }
+};
+
 }  // namespace internal
 }  // namespace mojo