Implement unions as members of structs.

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

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import module as mojom
 
 # This module provides a mechanism for determining the packed order and offsets
 # of a mojom.Struct.
 #
 # ps = pack.PackedStruct(struct)
@@ skipping 27 matching lines @@
     mojom.UINT64:                8,
     mojom.DOUBLE:                8,
     mojom.STRING:                8,
     mojom.NULLABLE_STRING:       8
   }
 
   @classmethod
   def GetSizeForKind(cls, kind):
     if isinstance(kind, (mojom.Array, mojom.Map, mojom.Struct)):
       return 8
+    if isinstance(kind, mojom.Union):
+      return 16
     if (isinstance(kind, mojom.Interface) or
         isinstance(kind, mojom.InterfaceRequest)):
       kind = mojom.MSGPIPE
     if isinstance(kind, mojom.Enum):
       # TODO(mpcomplete): what about big enums?
       return cls.kind_to_size[mojom.INT32]
     if not kind in cls.kind_to_size:
       raise Exception("Invalid kind: %s" % kind.spec)
     return cls.kind_to_size[kind]
 
@@ skipping 161 matching lines @@
     # The fields are iterated in ordinal order here. However, the size of a
     # version is determined by the last field of that version in pack order,
     # instead of ordinal order. Therefore, we need to calculate the max value.
     last_payload_size = max(GetPayloadSizeUpToField(packed_field),
                             last_payload_size)
 
   assert len(versions) == 0 or last_num_fields != versions[-1].num_fields
   versions.append(VersionInfo(last_version, last_num_fields,
                               last_payload_size + HEADER_SIZE))
   return versions