Enable per thread heap for database thread

third_party/WebKit/Source/modules/webdatabase/DatabaseTracker.h

 /*
  * Copyright (C) 2007, 2008, 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
@@ skipping 56 matching lines @@
 
     void closeDatabasesImmediately(SecurityOrigin*, const String& name);
 
     using DatabaseCallback = Function<void(Database*)>;
     void forEachOpenDatabaseInPage(Page*, std::unique_ptr<DatabaseCallback>);
 
     void prepareToOpenDatabase(Database*);
     void failedToOpenDatabase(Database*);
 
 private:
-    using DatabaseSet = HashSet<UntracedMember<Database>>;
+    using DatabaseSet = HashSet<CrossThreadPersistent<Database>>;
     using DatabaseNameMap = HashMap<String, DatabaseSet*>;
     using DatabaseOriginMap = HashMap<String, DatabaseNameMap*>;
     class CloseOneDatabaseImmediatelyTask;
 
     DatabaseTracker();
 
     void closeOneDatabaseImmediately(const String& originIdentifier, const String& name, Database*);
 
     Mutex m_openDatabaseMapGuard;
 
-    // This map contains untraced pointers to a garbage-collected class. We can't
-    // make this traceable because it is updated by multiple database threads.
-    // See http://crbug.com/417990
     mutable OwnPtr<DatabaseOriginMap> m_openDatabaseMap;
 };
 
 } // namespace blink
 
 #endif // DatabaseTracker_h