Remove indexed_db_messages.h.

content/browser/indexed_db/mock_indexed_db_callbacks.cc

 // 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.
 
 #include "content/browser/indexed_db/mock_indexed_db_callbacks.h"
 
 #include <utility>
 
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 17 matching lines @@
 void MockIndexedDBCallbacks::OnSuccess(const std::vector<base::string16>&) {}
 
 void MockIndexedDBCallbacks::OnSuccess(const IndexedDBKey& key) {}
 
 void MockIndexedDBCallbacks::OnSuccess(
     std::unique_ptr<IndexedDBConnection> connection,
     const IndexedDBDatabaseMetadata& metadata) {
   connection_ = std::move(connection);
 }
 
-bool MockIndexedDBCallbacks::IsValid() const {
-  return true;
-}
-
 }  // namespace content