[IndexedDB] Refactoring to remove ref ptrs and host transaction ids.

content/browser/indexed_db/indexed_db_backing_store.h

Index: content/browser/indexed_db/indexed_db_backing_store.h
diff --git a/content/browser/indexed_db/indexed_db_backing_store.h b/content/browser/indexed_db/indexed_db_backing_store.h
index 48c46c060a960a367c1028e0ef568b0a9c83d78a..4c8ffa7ac85ccfe583204551e434c24535502469 100644
--- a/content/browser/indexed_db/indexed_db_backing_store.h
+++ b/content/browser/indexed_db/indexed_db_backing_store.h
@@ -19,6 +19,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "base/strings/string_piece.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
@@ -282,6 +283,8 @@ class CONTENT_EXPORT IndexedDBBackingStore
     // has been bumped, and journal cleaning should be deferred.
     bool committing_;
 
+    base::WeakPtrFactory<Transaction> ptr_factory_;
+
     DISALLOW_COPY_AND_ASSIGN(Transaction);
   };