IDL union: nullable support

Source/bindings/scripts/v8_union.py

Index: Source/bindings/scripts/v8_union.py
diff --git a/Source/bindings/scripts/v8_union.py b/Source/bindings/scripts/v8_union.py
index 2c4d735d6edcf6b44cd8428b70a220ff17a7e436..531573e8c6cfc582addfa1b7c1a283f5b7a9de74 100644
--- a/Source/bindings/scripts/v8_union.py
+++ b/Source/bindings/scripts/v8_union.py
@@ -16,12 +16,27 @@ header_forward_decls = set()
 
 
 def union_context(union_types, interfaces_info):
+    preprocessed_union_types = set()
+    nullable_union_types = set()
+    for union_type in union_types:
+        # Unwrap nullable if needed to avoid "OrNull" containers.
+        preprocessed_type = union_type.as_union_type
+        preprocessed_union_types.add(preprocessed_type)
+        if union_type.includes_nullable_type:
+            nullable_union_types.add(preprocessed_type)
+
+    preprocessed_union_types = sorted(preprocessed_union_types,
+                                      key=lambda union_type: union_type.name)
+    nullable_union_types = sorted(nullable_union_types,
+                                  key=lambda union_type: union_type.name)
     return {
         'containers': [container_context(union_type, interfaces_info)
-                       for union_type in union_types],
+                       for union_type in preprocessed_union_types],
         'cpp_includes': sorted(cpp_includes),
         'header_forward_decls': sorted(header_forward_decls),
         'header_includes': sorted(UNION_H_INCLUDES),
+        'nullable_containers': [nullable_container_context(union_type)
+                                for union_type in nullable_union_types],
     }
 
 
@@ -69,12 +84,20 @@ def container_context(union_type, interfaces_info):
         else:
             raise Exception('%s is not supported as an union member.' % member.name)
 
+    # Nullable restriction checks
+    nullable_members = union_type.number_of_nullable_member_types
+    if nullable_members > 1:
+        raise Exception('%s contains more than one nullable members' % union_type.name)
+    if dictionary_type and nullable_members == 1:
+        raise Exception('%s has a dictionary and a nullable member' % union_type.name)
+
     return {
         'array_buffer_type': array_buffer_type,
         'array_buffer_view_type': array_buffer_view_type,
         'boolean_type': boolean_type,
-        'cpp_class': union_type.name,
+        'cpp_class': union_type.cpp_type,
         'dictionary_type': dictionary_type,
+        'includes_nullable_type': union_type.includes_nullable_type,
         'interface_types': interface_types,
         'members': members,
         'needs_trace': any(member['is_traceable'] for member in members),
@@ -103,3 +126,9 @@ def member_context(member, interfaces_info):
         'v8_value_to_local_cpp_value': member.v8_value_to_local_cpp_value(
             {}, 'v8Value', 'cppValue', needs_exception_state_for_string=True),
     }
+
+
+def nullable_container_context(union_type):
+    return {
+        'cpp_class': union_type.cpp_type,
+    }