Password manager: Allow updating the Sync account password

Bug: 1110878
Change-Id: I92b45b1a8b97e4e00814886a66e646fb727681dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2333837
Commit-Queue: Marc Treib <treib@chromium.org>
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794621}

components/password_manager/core/browser/credentials_filter.h

@@ -16,10 +16,12 @@ class PasswordFormManager;
 // PasswordStore, etc.
 class CredentialsFilter {
  public:
-  CredentialsFilter() {}
-  virtual ~CredentialsFilter() {}
+  CredentialsFilter() = default;
+  virtual ~CredentialsFilter() = default;
 
   // Should |form| be offered to be saved?
+  // Note that this only refers to *saving* - *updating* an already stored
+  // credential should still be allowed even if this returns false!
   virtual bool ShouldSave(const autofill::PasswordForm& form) const = 0;
 
   // Returns true if the hash of the password in |form| should be saved for Gaia

components/password_manager/core/browser/password_manager.cc

@@ -931,7 +931,12 @@ void PasswordManager::OnLoginSuccessful() {
 
   // TODO(https://crbug.com/831123): Implement checking whether to save with
   // PasswordFormManager.
-  if (!client_->GetStoreResultFilter()->ShouldSave(
+  // Check whether the filter allows saving this credential. In practice, this
+  // prevents saving the password of the syncing account. However, if the
+  // password is already saved, then *updating* it is still allowed - better
+  // than keeping an outdated password around.
+  if (!submitted_manager->IsPasswordUpdate() &&
+      !client_->GetStoreResultFilter()->ShouldSave(
           *submitted_manager->GetSubmittedForm())) {
     RecordProvisionalSaveFailure(
         PasswordManagerMetricsRecorder::SYNC_CREDENTIAL,

components/password_manager/core/browser/sync_credentials_filter.cc

@@ -17,8 +17,6 @@
 #include "components/signin/public/identity_manager/identity_manager.h"
 #include "google_apis/gaia/gaia_auth_util.h"
 
-using autofill::PasswordForm;
-
 namespace password_manager {
 
 SyncCredentialsFilter::SyncCredentialsFilter(