PasswordManager: Use |typed_value| as a fallback if |value| is empty

There is a bug that the save prompt is not shown if the password value
is set as an empty value by JavaScript before form submitted. The bug is
a regression since crrev.com/c/2029514 (M81 stable), but it is enough
reasonable. So, this patch fixes FormParser instead of reverting the CL.

In the current implementation, FormParser is treated as parsing error if
|value| is empty. On the other hand, according to crrev.com/c/1404093,
if |typed_value| is present, we preferentially use it rather than
|value|. Similarly, this patch makes FormParser use |typed value|
preferentially even if |value| is empty.

Reproducible sites:
  - https://m.naver.com
  - https://zino.dev (This is a minimal test page I wrote)

Bug: 1042196
Change-Id: I6652822fd7fe268b54647434c23c68d41abf5010
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2154644Reviewed-by: Vadym Doroshenko  <dvadym@chromium.org>
Commit-Queue: Vadym Doroshenko  <dvadym@chromium.org>
Cr-Commit-Position: refs/heads/master@{#760543}

components/password_manager/core/browser/form_parsing/form_parser.cc

@@ -229,7 +229,7 @@ bool IsProbablyNotUsername(const base::string16& s) {
 }
 
 // Returns |typed_value| if it is not empty, |value| otherwise.
-base::string16 GetFieldValue(const FormFieldData& field) {
+const base::string16& GetFieldValue(const FormFieldData& field) {
   return field.typed_value.empty() ? field.value : field.typed_value;
 }
 
@@ -554,7 +554,7 @@ std::vector<const FormFieldData*> GetRelevantPasswords(
   if (mode == FormDataParser::Mode::kSaving) {
     // Step 2: apply filter criterion (2).
     base::EraseIf(passwords, [](const ProcessedField* processed_field) {
-      return processed_field->field->value.empty();
+      return GetFieldValue(*processed_field->field).empty();
     });
   }
 
@@ -875,21 +875,23 @@ std::vector<ProcessedField> ProcessFields(
   for (const FormFieldData& field : fields) {
     if (!field.IsTextInputElement())
       continue;
-    if (consider_only_non_empty && field.value.empty())
+
+    const base::string16& field_value = GetFieldValue(field);
+    if (consider_only_non_empty && field_value.empty())
       continue;
 
     const bool is_password = field.form_control_type == "password";
 
-    if (!field.value.empty()) {
+    if (!field_value.empty()) {
       std::set<base::StringPiece16>& seen_values =
           is_password ? seen_password_values : seen_username_values;
       autofill::ValueElementVector* all_possible_fields =
           is_password ? all_possible_passwords : all_possible_usernames;
       // Only the field name of the first occurrence is added.
-      auto insertion = seen_values.insert(base::StringPiece16(field.value));
+      auto insertion = seen_values.insert(field_value);
       if (insertion.second) {
         // There was no such element in |seen_values|.
-        all_possible_fields->push_back({field.value, field.name});
+        all_possible_fields->push_back({field_value, field.name});
       }
     }
 

components/password_manager/core/browser/form_parsing/form_parser_unittest.cc

@@ -2412,29 +2412,54 @@ TEST(FormParserTest, GetSignonRealm) {
 }
 
 TEST(FormParserTest, TypedValues) {
-  CheckTestData({{
-      .description_for_logging = "Simple sign-in forms with typed values",
-      // Tests that typed values are taken as username, password and
-      // new password instead of values that are set by JavaScript.
-      .fields =
-          {
-              {.role = ElementRole::USERNAME,
-               .autocomplete_attribute = "username",
-               .value = "js_username",
-               .typed_value = "typed_username",
-               .form_control_type = "text"},
-              {.role = ElementRole::CURRENT_PASSWORD,
-               .autocomplete_attribute = "current-password",
-               .value = "js_password",
-               .typed_value = "typed_password",
-               .form_control_type = "password"},
-              {.role = ElementRole::NEW_PASSWORD,
-               .autocomplete_attribute = "new-password",
-               .value = "js_new_password",
-               .typed_value = "typed_new_password",
-               .form_control_type = "password"},
-          },
-  }});
+  CheckTestData({
+      {
+          .description_for_logging = "Form with changed by JavaScript values",
+          // Tests that typed values are taken as username, password and
+          // new password instead of values that are set by JavaScript.
+          .fields =
+              {
+                  {.role = ElementRole::USERNAME,
+                   .autocomplete_attribute = "username",
+                   .value = "js_username",
+                   .typed_value = "typed_username",
+                   .form_control_type = "text"},
+                  {.role = ElementRole::CURRENT_PASSWORD,
+                   .autocomplete_attribute = "current-password",
+                   .value = "js_password",
+                   .typed_value = "typed_password",
+                   .form_control_type = "password"},
+                  {.role = ElementRole::NEW_PASSWORD,
+                   .autocomplete_attribute = "new-password",
+                   .value = "js_new_password",
+                   .typed_value = "typed_new_password",
+                   .form_control_type = "password"},
+              },
+      },
+      {
+          .description_for_logging = "Form with cleared by JavaScript values",
+          // Tests that typed values are taken as username, password and
+          // new password instead of values that are cleared by JavaScript.
+          .fields =
+              {
+                  {.role = ElementRole::USERNAME,
+                   .autocomplete_attribute = "username",
+                   .value = "",
+                   .typed_value = "typed_username",
+                   .form_control_type = "text"},
+                  {.role = ElementRole::CURRENT_PASSWORD,
+                   .autocomplete_attribute = "current-password",
+                   .value = "",
+                   .typed_value = "typed_password",
+                   .form_control_type = "password"},
+                  {.role = ElementRole::NEW_PASSWORD,
+                   .autocomplete_attribute = "new-password",
+                   .value = "",
+                   .typed_value = "typed_new_password",
+                   .form_control_type = "password"},
+              },
+      },
+  });
 }
 
 TEST(FormParserTest, ContradictingPasswordPredictionAndAutocomplete) {