[IndexedDB] Pool and evict leveldb iterators, to save memory

content/browser/indexed_db/indexed_db_backing_store.cc

Index: content/browser/indexed_db/indexed_db_backing_store.cc
diff --git a/content/browser/indexed_db/indexed_db_backing_store.cc b/content/browser/indexed_db/indexed_db_backing_store.cc
index ffb0f8fc5f69577c84d32e8805a742aa6649faf5..cfd7d4b22286c374707328efba261312d6f90e3e 100644
--- a/content/browser/indexed_db/indexed_db_backing_store.cc
+++ b/content/browser/indexed_db/indexed_db_backing_store.cc
@@ -1064,7 +1064,9 @@ class DefaultLevelDBFactory : public LevelDBFactory {
                      const LevelDBComparator* comparator,
                      std::unique_ptr<LevelDBDatabase>* db,
                      bool* is_disk_full) override {
-    return LevelDBDatabase::Open(file_name, comparator, db, is_disk_full);
+    return LevelDBDatabase::Open(
+        file_name, comparator, db,
+        LevelDBDatabase::kDefaultMaxOpenIteratorsPerDatabase, is_disk_full);
   }
   Status DestroyLevelDB(const FilePath& file_name) override {
     return LevelDBDatabase::Destroy(file_name);