Allow Mojo structs as map keys

mojo/public/cpp/bindings/array.h

Index: mojo/public/cpp/bindings/array.h
diff --git a/mojo/public/cpp/bindings/array.h b/mojo/public/cpp/bindings/array.h
index a253da1f3954eed84541177cfee46df4c17a7dfa..8d74763ea975bf7b2b0ad3872fa52652135e27e4 100644
--- a/mojo/public/cpp/bindings/array.h
+++ b/mojo/public/cpp/bindings/array.h
@@ -17,6 +17,7 @@
 #include "mojo/public/cpp/bindings/lib/array_internal.h"
 #include "mojo/public/cpp/bindings/lib/bindings_internal.h"
 #include "mojo/public/cpp/bindings/lib/clone_equals_util.h"
+#include "mojo/public/cpp/bindings/lib/hash_util.h"
 #include "mojo/public/cpp/bindings/lib/template_util.h"
 #include "mojo/public/cpp/bindings/type_converter.h"
 
@@ -182,6 +183,10 @@ class Array {
     return internal::Equals(vec_, other.vec_);
   }
 
+  size_t Hash(size_t seed) const {
+    return is_null() ? seed : internal::Hash(seed, vec_);
+  }
+
  private:
   typedef std::vector<T> Array::*Testable;