Avoid using declarations in headers which introduce symbol conflicts.

third_party/WebKit/Source/modules/indexeddb/InspectorIndexedDBAgent.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 50 matching lines @@
 #include "wtf/Vector.h"
 
 using blink::protocol::Array;
 using blink::protocol::IndexedDB::DatabaseWithObjectStores;
 using blink::protocol::IndexedDB::DataEntry;
 using blink::protocol::IndexedDB::Key;
 using blink::protocol::IndexedDB::KeyPath;
 using blink::protocol::IndexedDB::KeyRange;
 using blink::protocol::IndexedDB::ObjectStore;
 using blink::protocol::IndexedDB::ObjectStoreIndex;
+using blink::protocol::Maybe;
+using blink::protocol::Response;
 
 typedef blink::protocol::IndexedDB::Backend::RequestDatabaseNamesCallback
     RequestDatabaseNamesCallback;
 typedef blink::protocol::IndexedDB::Backend::RequestDatabaseCallback
     RequestDatabaseCallback;
 typedef blink::protocol::IndexedDB::Backend::RequestDataCallback
     RequestDataCallback;
 typedef blink::protocol::IndexedDB::Backend::ClearObjectStoreCallback
     ClearObjectStoreCallback;
 typedef blink::protocol::IndexedDB::Backend::DeleteDatabaseCallback
@@ skipping 946 matching lines @@
                              document->getSecurityOrigin()->toRawString()),
       false);
 }
 
 DEFINE_TRACE(InspectorIndexedDBAgent) {
   visitor->trace(m_inspectedFrames);
   InspectorBaseAgent::trace(visitor);
 }
 
 }  // namespace blink