IndexedDB: Optimize IDBCursor.advance() if it occurs within prefetched range

content/child/indexed_db/webidbcursor_impl.h

 // Copyright 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.
 
 #ifndef CONTENT_CHILD_INDEXED_DB_PROXY_WEBIDBCURSOR_IMPL_H_
 #define CONTENT_CHILD_INDEXED_DB_PROXY_WEBIDBCURSOR_IMPL_H_
 
 #include <deque>
 #include <vector>
 
@@ skipping 22 matching lines @@
                                 blink::WebIDBCallbacks* callback);
   virtual void continueFunction(const blink::WebIDBKey& key,
                                 const blink::WebIDBKey& primary_key,
                                 blink::WebIDBCallbacks* callback);
   virtual void postSuccessHandlerCallback();
 
   void SetPrefetchData(const std::vector<IndexedDBKey>& keys,
                        const std::vector<IndexedDBKey>& primary_keys,
                        const std::vector<blink::WebData>& values);
 
+  void CachedAdvance(unsigned long count, blink::WebIDBCallbacks* callbacks);
   void CachedContinue(blink::WebIDBCallbacks* callbacks);
   void ResetPrefetchCache();
 
  private:
   FRIEND_TEST_ALL_PREFIXES(WebIDBCursorImplTest, PrefetchTest);
+  FRIEND_TEST_ALL_PREFIXES(WebIDBCursorImplTest, AdvancePrefetchTest);
 
   int32 ipc_cursor_id_;
 
   // Prefetch cache.
   std::deque<IndexedDBKey> prefetch_keys_;
   std::deque<IndexedDBKey> prefetch_primary_keys_;
   std::deque<blink::WebData> prefetch_values_;
 
   // Number of continue calls that would qualify for a pre-fetch.
   int continue_count_;
@@ skipping 11 matching lines @@
 
   enum { kInvalidCursorId = -1 };
   enum { kPrefetchContinueThreshold = 2 };
   enum { kMinPrefetchAmount = 5 };
   enum { kMaxPrefetchAmount = 100 };
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_INDEXED_DB_PROXY_WEBIDBCURSOR_IMPL_H_