Have field ordering for method parameters and response starts at 0.

With the current implementation, the field ordering start with 1, while
it must starts with 0 for structs.

R=davemoore@chromium.org

Review URL: https://codereview.chromium.org/252633007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@266774 0039d316-1c4b-4281-b951-d872f2087c98

mojo/public/tools/bindings/pylib/mojom/generate/pack.py

@@ -81,7 +81,7 @@ class PackedStruct(object):
 
     # Start by sorting by ordinal.
     src_fields = []
-    ordinal = 1
+    ordinal = 0
     for field in struct.fields:
       if field.ordinal is not None:
         ordinal = field.ordinal