[Passwords] Add Feature to Control reparsing of Server Predictions

This change adds a feature flag to control reparsing server predictions
following dynamic form changes.

Bug: 1140480
Change-Id: Ic0520f197d766fedab96c5c30d089bba49ef3e23
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2534857Reviewed-by: Maria Kazinova <kazinova@google.com>
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826884}

components/password_manager/core/browser/password_form_manager.cc

@@ -100,6 +100,13 @@ bool FormContainsFieldWithName(const FormData& form,
   return false;
 }
 
+// Returns whether reparsing server predictions following a form change is
+// enabled.
+bool IsReparsingServerPredictionsEnabled() {
+  return base::FeatureList::IsEnabled(
+      features::kReparseServerPredictionsFollowingFormChange);
+}
+
 bool IsUsernameFirstFlowFeatureEnabled() {
   return base::FeatureList::IsEnabled(features::kUsernameFirstFlow);
 }
@@ -831,7 +838,8 @@ void PasswordFormManager::FillForm(
   bool new_predictions_available = false;
   if (differences_bitmask) {
     UpdateFormManagerWithFormChanges(observed_form_data, predictions);
-    new_predictions_available = parser_.predictions().has_value();
+    new_predictions_available =
+        parser_.predictions() && IsReparsingServerPredictionsEnabled();
   }
   // Fill the form if relevant form predictions were found or if the
   // manager is not waiting for new server predictions.
@@ -1076,6 +1084,9 @@ void PasswordFormManager::UpdateFormManagerWithFormChanges(
     const FormData& observed_form_data,
     const std::map<FormSignature, FormPredictions>& predictions) {
   *mutable_observed_form() = observed_form_data;
+  if (!IsReparsingServerPredictionsEnabled())
+    return;
+
   // If the observed form has changed, it might be autofilled again.
   autofills_left_ = kMaxTimesAutofill;
   parser_.reset_predictions();

components/password_manager/core/browser/password_manager_unittest.cc

@@ -3667,6 +3667,12 @@ TEST_P(PasswordManagerTest,
 }
 
 TEST_P(PasswordManagerTest, GenerationOnChangedForm) {
+  const bool kIsReparsingEnabled = GetParam();
+  base::test::ScopedFeatureList feature_list;
+  feature_list.InitWithFeatureState(
+      features::kReparseServerPredictionsFollowingFormChange,
+      kIsReparsingEnabled);
+
   EXPECT_CALL(client_, IsSavingAndFillingEnabled(_))
       .WillRepeatedly(Return(true));
   EXPECT_CALL(*store_, GetLogins(_, _))
@@ -3706,12 +3712,16 @@ TEST_P(PasswordManagerTest, GenerationOnChangedForm) {
   manager()->ProcessAutofillPredictions(&driver_, {&form_structure});
 
   autofill::PasswordFormGenerationData form_generation_data;
-  EXPECT_CALL(driver_, FormEligibleForGenerationFound(_))
-      .WillOnce(SaveArg<0>(&form_generation_data));
-  // The change is discovered by PasswordManager.
-  manager()->OnPasswordFormsParsed(&driver_, {form_data});
-  EXPECT_EQ(new_password_field.unique_renderer_id,
-            form_generation_data.new_password_renderer_id);
+  if (kIsReparsingEnabled) {
+    EXPECT_CALL(driver_, FormEligibleForGenerationFound)
+        .WillOnce(SaveArg<0>(&form_generation_data));
+    // The change is discovered by PasswordManager.
+    manager()->OnPasswordFormsParsed(&driver_, {form_data});
+    EXPECT_EQ(new_password_field.unique_renderer_id,
+              form_generation_data.new_password_renderer_id);
+  } else {
+    EXPECT_CALL(driver_, FormEligibleForGenerationFound).Times(0);
+  }
 }
 
 INSTANTIATE_TEST_SUITE_P(, PasswordManagerTest, testing::Bool());

components/password_manager/core/common/password_manager_features.cc

@@ -84,6 +84,12 @@ const base::Feature kPasswordsWeaknessCheck = {
 const base::Feature kRecoverFromNeverSaveAndroid = {
     "RecoverFromNeverSaveAndroid", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables reparsing server predictions once the password form manager notices a
+// dynamic form change.
+const base::Feature kReparseServerPredictionsFollowingFormChange = {
+    "ReparseServerPredictionsFollowingFormChange",
+    base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enables considering secondary server field predictions during form parsing.
 const base::Feature kSecondaryServerFieldPredictions = {
     "SecondaryServerFieldPredictions", base::FEATURE_DISABLED_BY_DEFAULT};

components/password_manager/core/common/password_manager_features.h

@@ -33,6 +33,7 @@ extern const base::Feature kPasswordImport;
 extern const base::Feature kPasswordScriptsFetching;
 extern const base::Feature kPasswordsWeaknessCheck;
 extern const base::Feature kRecoverFromNeverSaveAndroid;
+extern const base::Feature kReparseServerPredictionsFollowingFormChange;
 extern const base::Feature kSecondaryServerFieldPredictions;
 extern const base::Feature kTreatNewPasswordHeuristicsAsReliable;
 extern const base::Feature kUseOfHashAffiliationFetcher;