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

content/browser/indexed_db/indexed_db_backing_store_unittest.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 <stddef.h>
 #include <stdint.h>
 #include <utility>
 
@@ skipping 20 matching lines @@
 #include "storage/browser/quota/special_storage_policy.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/WebKit/public/platform/modules/indexeddb/WebIDBTypes.h"
 
 using base::ASCIIToUTF16;
 using url::Origin;
 
 namespace content {
 
 namespace {
+static const size_t kDefaultMaxOpenIteratorsPerDatabase = 50;
 
 // Write |content| to |file|. Returns true on success.
 bool WriteFile(const base::FilePath& file, base::StringPiece content) {
   int write_size = base::WriteFile(file, content.data(), content.length());
   return write_size >= 0 && write_size == static_cast<int>(content.length());
 }
 
 class Comparator : public LevelDBComparator {
  public:
   int Compare(const base::StringPiece& a,
               const base::StringPiece& b) const override {
     return content::Compare(a, b, false /*index_keys*/);
   }
   const char* Name() const override { return "idb_cmp1"; }
 };
 
 class DefaultLevelDBFactory : public LevelDBFactory {
  public:
   DefaultLevelDBFactory() {}
 
   leveldb::Status OpenLevelDB(const base::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,
+                                 kDefaultMaxOpenIteratorsPerDatabase, db,
+                                 is_disk_full);
   }
   leveldb::Status DestroyLevelDB(const base::FilePath& file_name) override {
     return LevelDBDatabase::Destroy(file_name);
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DefaultLevelDBFactory);
 };
 
 class TestableIndexedDBBackingStore : public IndexedDBBackingStore {
@@ skipping 1070 matching lines @@
 
   // Dictionary, message key and more.
   ASSERT_TRUE(WriteFile(info_path, "{\"message\":\"foo\",\"bar\":5}"));
   EXPECT_TRUE(
       IndexedDBBackingStore::ReadCorruptionInfo(path_base, origin, &message));
   EXPECT_FALSE(PathExists(info_path));
   EXPECT_EQ("foo", message);
 }
 
 }  // namespace content