[sync] Mark GetSyncablePrefsDatabase() as pure virtual

This CL wraps up a TODO to mark
PrefModelAssociatorClient::GetSyncablePrefsDatabase() as pure virtual
since all implementations have implemented it.

Bug: 1401271
Change-Id: I0f7538d508e88b3de4cff7055af3f3232fb3fb91
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4324042
Commit-Queue: Ankush Singh <ankushkush@google.com>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1116296}

components/sync_preferences/pref_model_associator_client.cc

@@ -3,24 +3,3 @@
 // found in the LICENSE file.
 
 #include "components/sync_preferences/pref_model_associator_client.h"
-#include "components/sync_preferences/syncable_prefs_database.h"
-
-namespace sync_preferences {
-namespace {
-// TODO(crbug.com/1401271): Remove this class once GetSyncablePrefsDatabase()
-// is marked as pure virtual.
-class DummySyncablePrefsDatabase : public SyncablePrefsDatabase {
- public:
-  bool IsPreferenceSyncable(const std::string& /*pref_name*/) const override {
-    return true;
-  }
-};
-}  // namespace
-
-const SyncablePrefsDatabase&
-PrefModelAssociatorClient::GetSyncablePrefsDatabase() const {
-  static const DummySyncablePrefsDatabase syncable_prefs_database;
-  return syncable_prefs_database;
-}
-
-}  // namespace sync_preferences

components/sync_preferences/pref_model_associator_client.h

@@ -43,9 +43,7 @@ class PrefModelAssociatorClient {
 
   // Returns a pointer to the instance of SyncablePrefsDatabase. This should
   // define the list of syncable preferences.
-  // TODO(crbug.com/1401271): Mark this method as pure virtual once
-  // platform-specific implementations are complete.
-  virtual const SyncablePrefsDatabase& GetSyncablePrefsDatabase() const;
+  virtual const SyncablePrefsDatabase& GetSyncablePrefsDatabase() const = 0;
 
  protected:
   PrefModelAssociatorClient() {}