Allow Mojo structs as map keys

mojo/public/interfaces/bindings/tests/test_structs.mojom

Index: mojo/public/interfaces/bindings/tests/test_structs.mojom
diff --git a/mojo/public/interfaces/bindings/tests/test_structs.mojom b/mojo/public/interfaces/bindings/tests/test_structs.mojom
index e3b0aff4c04b295094e029e1065b9845a9f6034d..cce90f626004d8562c80c9c0550ee84c42d63aef 100644
--- a/mojo/public/interfaces/bindings/tests/test_structs.mojom
+++ b/mojo/public/interfaces/bindings/tests/test_structs.mojom
@@ -126,6 +126,7 @@ struct MapKeyTypes {
   map<float, float> f9;
   map<double, double> f10;
   map<string, string> f11;
+  map<Rect, Rect> f12;
 };
 
 // Used to verify that various map value types can be encoded and decoded
@@ -386,3 +387,10 @@ struct ContainsInterfaceRequest {
 struct SingleBoolStruct {
   bool value;
 };
+
+// Used to verify that structs containing typemapped types can be hashed (if the
+// typemapped type itself is hashable).
+
+struct ContainsHashable {
+  Rect rect;
+};