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);
+  virtual void RequestIDBCursorAdvance(unsigned long count,

[alecflett, 2013/12/19 00:41:39]

I have been thrown off by this before, being virtual only for tests. Maybe a
comment (and in the next 2) indicating why they are virtual?

[jsbell, 2013/12/19 18:31:19]

Done.

+                                       blink::WebIDBCallbacks* callbacks_ptr,
+                                       int32 ipc_cursor_id);
 
   virtual void RequestIDBCursorContinue(const IndexedDBKey& key,
                                         const IndexedDBKey& primary_key,
                                         blink::WebIDBCallbacks* callbacks_ptr,
                                         int32 ipc_cursor_id);
 
   virtual void RequestIDBCursorPrefetch(int n,
                                         blink::WebIDBCallbacks* callbacks_ptr,
                                         int32 ipc_cursor_id);
 
@@ skipping 144 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_