Oilpan: Prepare to move AbstractSQLTransactionBackend, SQLTransactionBackend, and SQLTransactionCoo…

Source/modules/webdatabase/AbstractSQLTransactionBackend.h

Index: Source/modules/webdatabase/AbstractSQLTransactionBackend.h
diff --git a/Source/modules/webdatabase/AbstractSQLTransactionBackend.h b/Source/modules/webdatabase/AbstractSQLTransactionBackend.h
index f21f1cd3514814b7656be06ecda09e0301918c68..8745c0d7446e958efc66a8abd5e28ca9fe09e9a5 100644
--- a/Source/modules/webdatabase/AbstractSQLTransactionBackend.h
+++ b/Source/modules/webdatabase/AbstractSQLTransactionBackend.h
@@ -26,6 +26,7 @@
 #ifndef AbstractSQLTransactionBackend_h
 #define AbstractSQLTransactionBackend_h
 
+#include "heap/Handle.h"
 #include "modules/webdatabase/sqlite/SQLValue.h"
 #include "modules/webdatabase/AbstractSQLStatement.h"
 #include "modules/webdatabase/SQLError.h"
@@ -37,9 +38,10 @@
 
 namespace WebCore {
 
-class AbstractSQLTransactionBackend : public ThreadSafeRefCounted<AbstractSQLTransactionBackend> {
+class AbstractSQLTransactionBackend : public RefCountedWillBeGarbageCollectedFinalized<AbstractSQLTransactionBackend> {

[Mads Ager (chromium), 2014/03/18 13:57:10]

Is it OK to drop ThreadSafe here?

[tkent, 2014/03/19 04:44:56]

Yes.  ThreadSafeRefCounted means RefCountedBase::m_refCount can be accessed from
multiple threads. In this case, a context thread and a database thread.
GarbageCollected(Finalized) doesn't have m_refCount.

CrossThreadPersistent<SQLTransactionBackend> in DatabaseTask.h represents
(Abstract)SQLTransactionBackend can be shared in multiple threads.

[Mads Ager (chromium), 2014/03/19 06:30:54]

Yes, I know. However, you are using RefCountedWillBeGarbageCollectedFinalized so
this is RefCounted and not ThreadSafeRefCounted in the non-oilpan build. It
should remain ThreadSafeRefCounted in the non-oilpan build because it is
accessed from both context and database thread, right?

[tkent, 2014/03/19 06:33:47]

ah, got it.  This is my bad.  It should be
*ThreadSafe*RefCountedWillBeGarbageCollectedFinalized.

 public:
     virtual ~AbstractSQLTransactionBackend() { }
+    virtual void trace(Visitor*) = 0;
 
     virtual void requestTransitToState(SQLTransactionState) = 0;