Make the DatabaseTracker thread-safe.

WebCore/platform/sql/SQLiteDatabase.h

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
  *
  * 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 79 matching lines @@
     // FULL - Any writing calls to the DB block until the data is actually on the disk surface
     // NORMAL - SQLite pauses at some critical moments when writing, but much less than FULL
     // OFF - Calls return immediately after the data has been passed to disk
     enum SynchronousPragma { SyncOff = 0, SyncNormal = 1, SyncFull = 2 };
     void setSynchronous(SynchronousPragma);
     
     int lastError();
     const char* lastErrorMsg();
     
     sqlite3* sqlite3Handle() const {
-        ASSERT(currentThread() == m_openingThread);
+        ASSERT(m_sharable || currentThread() == m_openingThread);
         return m_db;
     }
     
     void setAuthorizer(PassRefPtr<DatabaseAuthorizer>);
 
     // (un)locks the database like a mutex
     void lock();
     void unlock();
     bool isAutoCommitOn() const;
 
+    // Set this flag to allow access from multiple threads.  Not all multi-threaded accesses are safe!
+    // See http://www.sqlite.org/cvstrac/wiki?p=MultiThreading for more info, and you must be running with compile flags and SQLite version appropriate
+    // to your cross-thread uses.
+    bool sharable() { return m_sharable; }
+    void setSharable(bool sharable) { m_sharable = sharable; }
+
 private:
     static int authorizerFunction(void*, int, const char*, const char*, const char*, const char*);
 
     void enableAuthorizer(bool enable);
     
     int pageSize();
     
     sqlite3* m_db;
     int m_lastError;
     int m_pageSize;
     
     bool m_transactionInProgress;
+    bool m_sharable;
     
     Mutex m_authorizerLock;
     RefPtr<DatabaseAuthorizer> m_authorizer;
 
     Mutex m_lockingMutex;
     ThreadIdentifier m_openingThread;
     
 }; // class SQLiteDatabase
 
 } // namespace WebCore
 
 #endif