Fix typo in iOS autofill js: s/fieldset/fieldsets/

In the getUnownedAutofillableFormFieldElements_() function for iOS
autofill, inside a conditional that is triggered if a <fieldset> is not
a descendant of a <form> element, there is a line that appends an element
to a non-existant variable `fieldset` when it is clear that `fieldsets`
is what was intended.

BUG=570095
R=jif@chromium.org

Review-Url: https://codereview.chromium.org/2343013005
Cr-Commit-Position: refs/heads/master@{#419498}

AUTHORS

@@ -208,6 +208,7 @@ Finbar Crago <finbar.crago@gmail.com>
 François Beaufort <beaufort.francois@gmail.com>
 Francois Kritzinger <francoisk777@gmail.com>
 Francois Rauch <leopardb@gmail.com>
+Frankie Dintino <fdintino@theatlantic.com>
 Frédéric Jacob <frederic.jacob.78@gmail.com>
 Frédéric Wang <fred.wang@free.fr>
 Gaetano Mendola <mendola@gmail.com>

components/autofill/ios/browser/resources/autofill_controller.js

@@ -265,7 +265,7 @@ function getUnownedAutofillableFormFieldElements_(elements, fieldsets) {
 
     if (__gCrWeb.autofill.hasTagName(elements[i], 'fieldset') &&
         !isElementInsideFormOrFieldSet(elements[i])) {
-      fieldset.push(elements[i]);
+      fieldsets.push(elements[i]);
     }
   }
   return __gCrWeb.autofill.extractAutofillableElementsFromSet(