Various follow-up fixes to whatwg#180.

Fix distinguishable algorithm. Closes whatwg#190.
Fix record handling in various algorithms. Closes whatwg#191, closes whatwg#189.

index.bs

@@ -3253,7 +3253,7 @@ extended attribute’s [=takes a named argument list|named argument list=].
 </div>
 
 Two types are <dfn id="dfn-distinguishable" export>distinguishable</dfn> if
-at most one of the two [=includes a nullable type=]
+at most one of the two [=includes a nullable type=], is a [=dictionary type=], or a [=record type=],
 and at least one of the following three conditions is true:
 
 1.  The two types (taking their [=inner types=]
@@ -7758,12 +7758,11 @@ represented by ECMAScript values that correspond to the union’s
     1.  Let |types| be the [=flattened member types=]
         of the [=union type=].
     1.  If |V| is <emu-val>null</emu-val> or
-        <emu-val>undefined</emu-val>, and
-        |types| includes a
-        [=dictionary type=], then return the
-        result of
-        [=converted to an IDL value|converting=]
-        |V| to that dictionary type.
+        <emu-val>undefined</emu-val>, then:
+        1.  If |types| includes a [=dictionary type=], then return the
+            result of [=converted to an IDL value|converting=] |V| to that dictionary type.
+        1.  If |types| includes a [=record type=], then return the
+            result of [=converted to an IDL value|converting=] |V| to that record type.
     1.  If |V| is a [=platform object=], then:
         1.  If |types| includes an [=interface type=] that |V|
             implements, then return the IDL value that is a reference to the object |V|.
@@ -9990,7 +9989,7 @@ and a list of IDL values or the special value “missing”.  The algorithm beha
             *   a [=record type=]
             *   a [=union type=] that
                 [=includes a nullable type=] or that
-                has a [=dictionary type=] in its [=flattened member types|flattened members=]
+                has a [=dictionary type=] or a [=record type=] in its [=flattened member types|flattened members=]
 
             then remove from |S| all other entries.