bind-gen: Effectively remove named definer from HTML{Embed,Object}Element

In order to route the property access to the platform objects to
the embedding objects, HTMLEmbedElement and HTMLObjectElement are
(ab)using the named properties, hence the regular definition of
[[DefineOwnProperty]] of named properties shouldn't be applied.
(By the way, the situation is similar to CSS properties.)

This patch makes NamedPropertyDefinerCallback noop in case of
HTMLEmbedElement and HTMLObjectElement.

Bug: 1139312, 839389
Change-Id: I5089965ad766440920e4cc2d3308a2e2fae4250b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2481163Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818395}

third_party/blink/renderer/bindings/scripts/bind_gen/interface.py

@@ -2942,6 +2942,13 @@ def make_named_property_definer_callback(cg_context, function_name):
             TextNode("""\
 // CSSStyleDeclaration is abusing named properties.
 // Do not intercept.  Fallback to OrdinaryDefineOwnProperty.
+"""))
+    elif cg_context.interface.identifier in ("HTMLEmbedElement",
+                                             "HTMLObjectElement"):
+        body.append(
+            TextNode("""\
+// HTMLEmbedElement and HTMLObjectElement are abusing named properties.
+// Do not intercept.  Fallback to OrdinaryDefineOwnProperty.
 """))
     elif not cg_context.interface.indexed_and_named_properties.named_setter:
         body.append(
@@ -2986,17 +2993,7 @@ if (v8_property_desc.has_get() || v8_property_desc.has_set()) {
   }
   return;
 }
-"""))
-        if cg_context.interface.identifier in ("HTMLEmbedElement",
-                                               "HTMLObjectElement"):
-            body.append(
-                TextNode("""\
-// HTMLEmbedElement and HTMLObjectElement's named properties implementation
-// depend on the default fallback behavior.  So, just fallback.
-"""))
-        else:
-            body.append(
-                TextNode("""\
+
 // step 2.2.2.2. Invoke the named property setter with P and Desc.[[Value]].
 ${class_name}::NamedPropertySetterCallback(
     ${v8_property_name}, ${v8_property_desc}.value(), ${info});