buffet: Provide results definition in command definition.

That allows us to provide typed results for supported commands.

BUG=chromium:435607
TEST=cros_workon_make --test buffet

Change-Id: I61b5a5b294b4d869366c821adf1ef7f6db31c7ea
Reviewed-on: https://chromium-review.googlesource.com/231322
Reviewed-by: Anton Muhin <antonm@chromium.org>
Commit-Queue: Anton Muhin <antonm@chromium.org>
Tested-by: Anton Muhin <antonm@chromium.org>
diff --git a/buffet/commands/schema_constants.cc b/buffet/commands/schema_constants.cc
index faf58fb..a26c355 100644
--- a/buffet/commands/schema_constants.cc
+++ b/buffet/commands/schema_constants.cc
@@ -46,6 +46,7 @@
 const char kCommand_Id[] = "id";
 const char kCommand_Name[] = "name";
 const char kCommand_Parameters[] = "parameters";
+const char kCommand_Results[] = "results";
 }  // namespace attributes
 }  // namespace commands