Remove SyncPrefs::GetLocalSyncBackendDir

It's unused - in practice, the value is queried through
SyncClient::GetLocalSyncBackendFolder (which contains some extra logic).

Bug: none
Change-Id: Icc2dc605ea66ba86f6e6055c126739c37efbcb05
Reviewed-on: https://chromium-review.googlesource.com/c/1290275Reviewed-by: vitaliii <vitaliii@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601111}

components/sync/base/sync_prefs.cc

@@ -595,8 +595,4 @@ bool SyncPrefs::IsLocalSyncEnabled() const {
   return local_sync_enabled_;
 }
 
-base::FilePath SyncPrefs::GetLocalSyncBackendDir() const {
-  return pref_service_->GetFilePath(prefs::kLocalSyncBackendDir);
-}
-
 }  // namespace syncer

components/sync/base/sync_prefs.h

@@ -216,9 +216,8 @@ class SyncPrefs : public CryptoSyncPrefs,
   void GetNigoriSpecificsForPassphraseTransition(
       sync_pb::NigoriSpecifics* nigori_specifics) const override;
 
-  // Gets the local sync backend enabled state and its database location.
+  // Gets the local sync backend enabled state.
   bool IsLocalSyncEnabled() const;
-  base::FilePath GetLocalSyncBackendDir() const;
 
   // Returns a ModelTypeSet based on |types| expanded to include pref groups
   // (see |pref_groups_|), but as a subset of |registered_types|.