[Sync] Replace ClearServerDataCallback with Closure.

components/sync/engine/fake_sync_manager.cc

Index: components/sync/engine/fake_sync_manager.cc
diff --git a/components/sync/engine/fake_sync_manager.cc b/components/sync/engine/fake_sync_manager.cc
index e9f9ce8b1f5556b8a771eb243c0a0d3099a77054..2d985b013ddf3bcc75b7377e4312c6f2bb7c78c9 100644
--- a/components/sync/engine/fake_sync_manager.cc
+++ b/components/sync/engine/fake_sync_manager.cc
@@ -260,7 +260,7 @@ void FakeSyncManager::SetInvalidatorEnabled(bool invalidator_enabled) {
   // Do nothing.
 }
 
-void FakeSyncManager::ClearServerData(const ClearServerDataCallback& callback) {
+void FakeSyncManager::ClearServerData(const base::Closure& callback) {
   callback.Run();
 }