Add password form search using blink::WebNode reference comparison.

components/autofill/content/renderer/form_autofill_util.cc

Index: components/autofill/content/renderer/form_autofill_util.cc
diff --git a/components/autofill/content/renderer/form_autofill_util.cc b/components/autofill/content/renderer/form_autofill_util.cc
index 9677f8c184a7bfb23fe3f38e50ed461c3b9d9150..deea51c1a8332eb1af0000ac9a48106a25b40298 100644
--- a/components/autofill/content/renderer/form_autofill_util.cc
+++ b/components/autofill/content/renderer/form_autofill_util.cc
@@ -1203,6 +1203,7 @@ bool ExtractFormData(const WebFormElement& form_element, FormData* data) {
 }
 
 bool IsFormVisible(blink::WebFrame* frame,
+                   const blink::WebFormElement& form_element,
                    const GURL& canonical_action,
                    const GURL& canonical_origin,
                    const FormData& form_data) {
@@ -1232,6 +1233,11 @@ bool IsFormVisible(blink::WebFrame* frame,
     if (action_is_empty != form_action_is_empty)
       continue;
 
+    // Try to match the WebFormElement reference first.

[dvadym, 2017/03/14 17:11:10]

I think it's better to move up these lines before checking whether action is
empty or not. In such way we can be robust against JavaScript add/remove action

[sense (YandexTeam), 2017/03/15 04:51:24]

Yes, I agree.

+    if (!form_element.isNull() && form.equals(form_element)) {

[dvadym, 2017/03/14 17:11:10]

Nit: you can use == operator (form == form_element). That's used more frequent
then equal.

+      return true;  // Form still exists.
+    }
+
     if (action_is_empty) {  // Both actions are empty, compare all fields.
       FormData extracted_form_data;
       WebFormElementToFormData(form, WebFormControlElement(), nullptr,