Some fleshing out the mojo based localstorage implementation.

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 f522faab532a4d5d6276098cfc8fd907835b0471..e9bd6838412e94fcd927f58637e98e1faa44d66f 100644
--- a/mojo/public/cpp/bindings/array.h
+++ b/mojo/public/cpp/bindings/array.h
@@ -295,6 +295,16 @@ struct TypeConverter<std::set<E>, Array<T>> {
   }
 };
 
+// Less than operator to allow Arrays as keys in std maps and sets.
+template <typename T>
+inline bool operator<(const Array<T>& a, const Array<T>& b) {
+  if (a.is_null())
+    return !b.is_null();
+  if (b.is_null())
+    return false;
+  return a.storage() < b.storage();
+}
+
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_ARRAY_H_