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

content/browser/indexed_db/indexed_db_backing_store.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/indexed_db/indexed_db_backing_store.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/files/file_path.h"
@@ skipping 1046 matching lines @@
 
 }  // namespace
 
 class DefaultLevelDBFactory : public LevelDBFactory {
  public:
   DefaultLevelDBFactory() {}
   Status OpenLevelDB(const FilePath& file_name,
                      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,
+        LevelDBDatabase::kDefaultMaxOpenIteratorsPerDatabase, db, is_disk_full);
   }
   Status DestroyLevelDB(const FilePath& file_name) override {
     return LevelDBDatabase::Destroy(file_name);
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DefaultLevelDBFactory);
 };
 
 IndexedDBBackingStore::IndexedDBBackingStore(
@@ skipping 3376 matching lines @@
 
 IndexedDBBackingStore::Transaction::WriteDescriptor::WriteDescriptor(
     const WriteDescriptor& other) = default;
 IndexedDBBackingStore::Transaction::WriteDescriptor::~WriteDescriptor() =
     default;
 IndexedDBBackingStore::Transaction::WriteDescriptor&
     IndexedDBBackingStore::Transaction::WriteDescriptor::
     operator=(const WriteDescriptor& other) = default;
 
 }  // namespace content