[TransactionalLevelDB] Fix memory dump provider

During a refactor, the filename used for memory dumps was dropped. This
fixes that.

R=rockot@chromium.org

Bug: 1028623
Change-Id: I439eff20e0ddd19329a100a84be33dcd5f482073
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1951779
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Ken Rockot <rockot@google.com>
Auto-Submit: Daniel Murphy <dmurph@chromium.org>
Reviewed-by: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#721780}

components/services/storage/indexed_db/transactional_leveldb/transactional_leveldb_database.cc

@@ -268,7 +268,7 @@ bool TransactionalLevelDBDatabase::OnMemoryDump(
     return true;
   }
 
-  db_dump->AddString("file_name", "", file_name_for_tracing);
+  db_dump->AddString("file_name", "", level_db_state_->name_for_tracing());
 
   return true;
 }

components/services/storage/indexed_db/transactional_leveldb/transactional_leveldb_database.h

@@ -170,8 +170,6 @@ class TransactionalLevelDBDatabase
   uint32_t num_iterators_ = 0;
   uint32_t max_iterators_ = 0;
 
-  std::string file_name_for_tracing;
-
   base::WeakPtrFactory<TransactionalLevelDBDatabase>
       weak_factory_for_iterators_{this};
 };