IDL parser: Make AsyncIterable independent from Iterable

"async iterable" and "iterable" are literally similar, but
have different definitions in spec.
And it provides us following benefit to separate "async iterable"
and "iterable";
- It makes easy to dispatch different functions in the code generator.
  https://cs.chromium.org/chromium/src/third_party/blink/renderer/bindings/scripts/web_idl/ir_builder.py?q=ir_builder&dr&l=104&rcl=489221aa216913b574354b09ff94469151b682b4
  is a bad example that comes from setting "callback" property on "interface" node.
- Current code generators do not support "async iterable", but they accidentally accept
  it as "(synchronous) iterable" without throwing errors.  This CL makes it an error.


Bug: 839389
Change-Id: Ie48829802ac2a73916ba081459208c0d11f13740
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1855540
Commit-Queue: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705022}

tools/idl_parser/idl_parser.py

@@ -670,8 +670,7 @@ class IDLParser(object):
   def p_AsyncIterable(self, p):
     """AsyncIterable : ASYNC ITERABLE '<' TypeWithExtendedAttributes ',' TypeWithExtendedAttributes '>' ';'"""
     childlist = ListFromConcat(p[4], p[6])
-    p[0] = self.BuildProduction('Iterable', p, 2, childlist)
-    p[0].AddChildren(self.BuildTrue('ASYNC'))
+    p[0] = self.BuildProduction('AsyncIterable', p, 2, childlist)
 
   def p_ReadWriteMaplike(self, p):
     """ReadWriteMaplike : MaplikeRest"""

tools/idl_parser/test_parser/interface_web.idl

@@ -436,8 +436,7 @@ interface MyIfacePromise {
  *      PrimitiveType(long long)
  *      ExtAttributes()
  *        ExtAttribute(EnforceRange)
- *  Iterable()
- *    ASYNC: True
+ *  AsyncIterable()
  *    Type()
  *      PrimitiveType(double)
  *    Type()