[AF] Remove ununsed web data service observer notification

This CL removes and unused notification AutofillMultipleChangedBySync()
from the AutofillWebDataServiceObserverOnDBSequence interface.

#JointFixit

Bug: 900607
Change-Id: I03d32a60f7fbac58a3738767baead7fe61354d34
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1824091
Commit-Queue: Jan Krcal <jkrcal@chromium.org>
Commit-Queue: Vadym Doroshenko <dvadym@chromium.org>
Auto-Submit: Jan Krcal <jkrcal@chromium.org>
Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699871}

components/autofill/core/browser/webdata/autofill_webdata_backend_impl.cc

@@ -117,10 +117,6 @@ void AutofillWebDataBackendImpl::NotifyOfCreditCardChanged(
 void AutofillWebDataBackendImpl::NotifyOfMultipleAutofillChanges() {
   DCHECK(owning_task_runner()->RunsTasksInCurrentSequence());
 
-  // DB sequence notification.
-  for (auto& db_observer : db_observer_list_)
-    db_observer.AutofillMultipleChangedBySync();
-
   // UI sequence notification.
   ui_task_runner_->PostTask(FROM_HERE, on_changed_callback_);
 }

components/autofill/core/browser/webdata/autofill_webdata_service_observer.h

@@ -23,13 +23,6 @@ class AutofillWebDataServiceObserverOnDBSequence {
   // the WebDatabase.
   virtual void CreditCardChanged(const CreditCardChange& change) {}
 
-  // Called on DB sequence when multiple Autofill entries have been modified by
-  // Sync.
-  // TODO(crbug.com/900607): Remove AutofillMultipleChangedBySync() from
-  // AutofillWebDataServiceObserverOnDBSequence once USS for wallet_metadata
-  // launches.
-  virtual void AutofillMultipleChangedBySync() {}
-
  protected:
   virtual ~AutofillWebDataServiceObserverOnDBSequence() {}
 };