Bug 1361560 - Force experimental autocomplete pref on during wpt DOM interface test. r=jgraham,jessica

Since the pref is enabled for Nightly-only for now, have the WPT test force it on so that
it doesn't fail at merge day.

MozReview-Commit-ID: 3MCRRqBZ5CM

--HG--
extra : rebase_source : 74c0ff8edd109a055dcff65f9238ca2f82820536

testing/web-platform/meta/html/dom/interfaces.html.ini

@@ -1,6 +1,6 @@
 [interfaces.html]
   type: testharness
-  prefs: [dom.forms.inputmode:true, dom.dialog_element.enabled:true]
+  prefs: [dom.forms.inputmode:true, dom.dialog_element.enabled:true, dom.forms.autocomplete.experimental:true]
   [Document interface: attribute domain]
     expected: FAIL
 
@@ -1123,15 +1123,9 @@
   [HTMLButtonElement interface: document.createElement("button") must inherit property "labels" with the proper type (18)]
     expected: FAIL
 
-  [HTMLSelectElement interface: attribute autocomplete]
-    expected: FAIL
-
   [HTMLSelectElement interface: attribute labels]
     expected: FAIL
 
-  [HTMLSelectElement interface: document.createElement("select") must inherit property "autocomplete" with the proper type (0)]
-    expected: FAIL
-
   [HTMLSelectElement interface: document.createElement("select") must inherit property "labels" with the proper type (26)]
     expected: FAIL