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

components/autofill/content/renderer/password_autofill_agent.h

Index: components/autofill/content/renderer/password_autofill_agent.h
diff --git a/components/autofill/content/renderer/password_autofill_agent.h b/components/autofill/content/renderer/password_autofill_agent.h
index 12b7d03c639ea26bf5a605469ef298e507a68a04..20f9c6aad5668f48aefca4c2ac702d5bf45f2ea7 100644
--- a/components/autofill/content/renderer/password_autofill_agent.h
+++ b/components/autofill/content/renderer/password_autofill_agent.h
@@ -14,6 +14,7 @@
 #include "components/autofill/content/common/autofill_driver.mojom.h"
 #include "components/autofill/content/renderer/autofill_agent.h"
 #include "components/autofill/content/renderer/password_form_conversion_utils.h"
+#include "components/autofill/content/renderer/provisionally_saved_password_form.h"
 #include "components/autofill/core/common/form_data_predictions.h"
 #include "components/autofill/core/common/password_form.h"
 #include "components/autofill/core/common/password_form_field_prediction_map.h"
@@ -239,15 +240,17 @@ class PasswordAutofillAgent : public content::RenderFrameObserver,
   void ClearPreview(blink::WebInputElement* username,
                     blink::WebInputElement* password);
 
-  // Saves |password_form| in |provisionally_saved_form_|, as long as it
-  // satisfies |restriction|.
+  // Saves |password_form|, |form| and |input| in |provisionally_saved_form_|,
+  // as long as it satisfies |restriction|. |form| and |input| are the elements
+  // user has just been interacting with before the form save. |form| or |input|
+  // can be null but not both at the same time. For example: if the form is
+  // unowned, |form| will be null; if the user has submitted the form, |input|
+  // will be null.
   void ProvisionallySavePassword(std::unique_ptr<PasswordForm> password_form,
+                                 const blink::WebFormElement& form,
+                                 const blink::WebInputElement& input,
                                  ProvisionallySaveRestriction restriction);
 
-  // Returns true if |provisionally_saved_form_| has enough information that
-  // it is likely filled out.
-  bool ProvisionallySavedPasswordIsValid();
-
   // Helper function called when in-page navigation completed
   void OnSamePageNavigationCompleted();
 
@@ -260,7 +263,7 @@ class PasswordAutofillAgent : public content::RenderFrameObserver,
 
   // Set if the user might be submitting a password form on the current page,
   // but the submit may still fail (i.e. doesn't pass JavaScript validation).
-  std::unique_ptr<PasswordForm> provisionally_saved_form_;
+  ProvisionallySavedPasswordForm provisionally_saved_form_;
 
   // Map WebFormControlElement to the pair of:
   // 1) The most recent text that user typed or PasswordManager autofilled in