IDL compiler: Fix constructor support for IDL namespace

Bug: 839389
Change-Id: I7fc344032d336977a7ff80e398dc2fcee6ccd156
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1873630
Commit-Queue: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708452}

third_party/blink/renderer/bindings/scripts/web_idl/idl_compiler_test.idl

@@ -10,3 +10,9 @@
   [Custom] constructor(Node node);
   [RuntimeEnabled=Hoge] constructor(long num);
 };
+
+namespace TestNamespace {
+  readonly attribute boolean attr1;
+  readonly attribute DOMString attr2;
+  void op1();
+};

third_party/blink/renderer/bindings/scripts/web_idl/namespace.py

@@ -62,6 +62,8 @@ class Namespace(UserDefinedType, WithExtendedAttributes, WithCodeGeneratorInfo,
             self.is_partial = is_partial
             self.attributes = list(attributes)
             self.constants = list(constants)
+            self.constructors = []
+            self.constructor_groups = []
             self.operations = list(operations)
             self.operation_groups = []