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

content/child/indexed_db/indexed_db_dispatcher.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_INDEXED_DB_DISPATCHER_H_
 #define CONTENT_CHILD_INDEXED_DB_INDEXED_DB_DISPATCHER_H_
 
 #include <map>
 #include <vector>
 
@@ skipping 64 matching lines @@
       int64 version,
       int64 transaction_id,
       blink::WebIDBCallbacks* callbacks,
       blink::WebIDBDatabaseCallbacks* database_callbacks,
       const std::string& database_identifier);
 
   void RequestIDBFactoryDeleteDatabase(const base::string16& name,
                                        blink::WebIDBCallbacks* callbacks,
                                        const std::string& database_identifier);
 
-  void RequestIDBCursorAdvance(unsigned long count,
-                               blink::WebIDBCallbacks* callbacks_ptr,
-                               int32 ipc_cursor_id);
+  // This method is virtual so it can be overridden in unit tests.
+  virtual void RequestIDBCursorAdvance(unsigned long count,
+                                       blink::WebIDBCallbacks* callbacks_ptr,
+                                       int32 ipc_cursor_id);
 
+  // This method is virtual so it can be overridden in unit tests.
   virtual void RequestIDBCursorContinue(const IndexedDBKey& key,
                                         const IndexedDBKey& primary_key,
                                         blink::WebIDBCallbacks* callbacks_ptr,
                                         int32 ipc_cursor_id);
 
+  // This method is virtual so it can be overridden in unit tests.
   virtual void RequestIDBCursorPrefetch(int n,
                                         blink::WebIDBCallbacks* callbacks_ptr,
                                         int32 ipc_cursor_id);
 
   void RequestIDBCursorPrefetchReset(int used_prefetches,
                                      int unused_prefetches,
                                      int32 ipc_cursor_id);
 
   void RequestIDBDatabaseClose(int32 ipc_database_id,
                                int32 ipc_database_callbacks_id);
@@ skipping 138 matching lines @@
   std::map<int32, WebIDBCursorImpl*> cursors_;
 
   std::map<int32, WebIDBDatabaseImpl*> databases_;
 
   DISALLOW_COPY_AND_ASSIGN(IndexedDBDispatcher);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_INDEXED_DB_INDEXED_DB_DISPATCHER_H_