Autofill: Disable autofill for fields outside of forms.

components/autofill/content/renderer/form_cache.h

Index: components/autofill/content/renderer/form_cache.h
diff --git a/components/autofill/content/renderer/form_cache.h b/components/autofill/content/renderer/form_cache.h
index d0c29cdaf8114a245a829d7b05dfa165be1e6c7c..f37a9817d5beeb27b31b815b1e697837e6da42e6 100644
--- a/components/autofill/content/renderer/form_cache.h
+++ b/components/autofill/content/renderer/form_cache.h
@@ -64,10 +64,6 @@ class FormCache {
   // The cached forms. Used to prevent re-extraction of forms.
   std::set<FormData> parsed_forms_;
 
-  // The synthetic FormData is for all the fieldsets in the document without a
-  // form owner.
-  FormData synthetic_form_;
-
   // The cached initial values for <select> elements.
   std::map<const blink::WebSelectElement, base::string16>
       initial_select_values_;