Remove duplicated headers from modules/ directory

Source/modules/webdatabase/DatabaseContext.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2011 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 22 matching lines @@
 #include "core/page/Chrome.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/Page.h"
 #include "core/page/Settings.h"
 #include "modules/webdatabase/Database.h"
 #include "modules/webdatabase/DatabaseManager.h"
 #include "modules/webdatabase/DatabaseTask.h"
 #include "modules/webdatabase/DatabaseThread.h"
 #include "platform/weborigin/SchemeRegistry.h"
 #include "platform/weborigin/SecurityOrigin.h"
+#include "wtf/Assertions.h"
 
 namespace WebCore {
 
 // How the DatabaseContext Life-Cycle works?
 // ========================================
 // ... in other words, who's keeping the DatabaseContext alive and how long does
 // it need to stay alive?
 //
 // The DatabaseContext is referenced from RefPtrs in:
 // 1. ExecutionContext
@@ skipping 154 matching lines @@
 {
     return executionContext()->securityOrigin();
 }
 
 bool DatabaseContext::isContextThread() const
 {
     return executionContext()->isContextThread();
 }
 
 } // namespace WebCore