Allow Mojo structs as map keys

mojo/public/cpp/bindings/lib/native_struct.cc

Index: mojo/public/cpp/bindings/lib/native_struct.cc
diff --git a/mojo/public/cpp/bindings/lib/native_struct.cc b/mojo/public/cpp/bindings/lib/native_struct.cc
index 837b75a60e3eb53031c78bcb8dfc946635b48123..2d60eb0d7e2b42d98b713af65dfd3d3655fc98b2 100644
--- a/mojo/public/cpp/bindings/lib/native_struct.cc
+++ b/mojo/public/cpp/bindings/lib/native_struct.cc
@@ -4,6 +4,8 @@
 
 #include "mojo/public/cpp/bindings/native_struct.h"
 
+#include "mojo/public/cpp/bindings/lib/hash_util.h"
+
 namespace mojo {
 
 // static
@@ -27,4 +29,8 @@ bool NativeStruct::Equals(const NativeStruct& other) const {
   return data.Equals(other.data);
 }
 
+size_t NativeStruct::Hash(size_t seed) const {
+  return internal::Hash(seed, data);
+}
+
 }  // namespace mojo