Remove worker support of Web SQL Database.

Source/modules/webdatabase/AbstractSQLTransactionBackend.h

 /*
  * Copyright (C) 2013 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 20 matching lines @@
 #include "modules/webdatabase/SQLError.h"
 #include "modules/webdatabase/SQLTransactionState.h"
 #include "platform/heap/Handle.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/ThreadSafeRefCounted.h"
 #include "wtf/Vector.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
+// FIXME: This abstraction is unnecessary because SQLTransactionBackendSync was
+// removed.
 class AbstractSQLTransactionBackend : public ThreadSafeRefCountedWillBeGarbageCollectedFinalized<AbstractSQLTransactionBackend> {
 public:
     virtual ~AbstractSQLTransactionBackend() { }
     virtual void trace(Visitor*) { }
 
     virtual void requestTransitToState(SQLTransactionState) = 0;
 
     virtual SQLErrorData* transactionError() = 0;
     virtual AbstractSQLStatement* currentStatement() = 0;
     virtual void setShouldRetryCurrentStatement(bool) = 0;
 
     virtual void executeSQL(PassOwnPtrWillBeRawPtr<AbstractSQLStatement>, const String& statement,
         const Vector<SQLValue>& arguments, int permissions) = 0;
 
 };
 
 } // namespace blink
 
 #endif // AbstractSQLTransactionBackend_h