[mojo-edk] Expose notification source to MojoWatch callbacks

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

Index: mojo/public/interfaces/bindings/tests/sample_interfaces.mojom
diff --git a/mojo/public/interfaces/bindings/tests/sample_interfaces.mojom b/mojo/public/interfaces/bindings/tests/sample_interfaces.mojom
index 5960d756657e79eb580b6fbaa28ae88f046430ef..fc1eebe9cbf2081017c80334e755bc3777404788 100644
--- a/mojo/public/interfaces/bindings/tests/sample_interfaces.mojom
+++ b/mojo/public/interfaces/bindings/tests/sample_interfaces.mojom
@@ -30,3 +30,11 @@ interface IntegerAccessor {
   [MinVersion=1]
   SetInteger(int64 data, [MinVersion=3] Enum type);
 };
+
+interface SingleMethod {
+  Call();
+};
+
+interface SingleMethodVendor {
+  GetCaller(associated SingleMethod& request);
+};