Wrap GCed raw pointer parameters of WTF::bind with Persistent

third_party/WebKit/Source/modules/webdatabase/DatabaseThread.cpp

Index: third_party/WebKit/Source/modules/webdatabase/DatabaseThread.cpp
diff --git a/third_party/WebKit/Source/modules/webdatabase/DatabaseThread.cpp b/third_party/WebKit/Source/modules/webdatabase/DatabaseThread.cpp
index e6bc6f22d9d7588ede778100b7fbb292b7c0537d..5fb519e7956f6f94a9b162512909b14879c2d3cf 100644
--- a/third_party/WebKit/Source/modules/webdatabase/DatabaseThread.cpp
+++ b/third_party/WebKit/Source/modules/webdatabase/DatabaseThread.cpp
@@ -114,7 +114,7 @@ void DatabaseThread::cleanupDatabaseThread()
     }
     m_openDatabaseSet.clear();
 
-    m_thread->postTask(BLINK_FROM_HERE, WTF::bind(&DatabaseThread::cleanupDatabaseThreadCompleted, this));
+    m_thread->postTask(BLINK_FROM_HERE, WTF::bind(&DatabaseThread::cleanupDatabaseThreadCompleted, wrapCrossThreadPersistent(this)));

[sof, 2016/06/22 09:39:22]

Isn't this happening on the same thread?

[tzik, 2016/06/22 10:16:01]

Yes, this task is posted to the same thread.
However, we need to use CrossThread here, since |this| is created on the main
thread and posted to the database thread.

[sof, 2016/06/22 13:24:27]

A Persistent<> is allowed to contain a reference to an object in another
thread's heap -- it only must be created & destroyed on the same thread. Which I
think will hold here + be a simpler rule to follow. Or did you discover
otherwise?

[tzik, 2016/06/22 13:56:51]

That's true on other threads than DatabaseThread.
According to keishi@, DatabaseThread recently starts using per-thread heap. That
requires all references from foreign threads to be CrossThread, so that GC
system can find it.

[sof, 2016/06/22 14:06:50]

If that's the case, how would |this| be discovered as a root for a main thread
GC while (e.g.) this method (cleanupDatabaseThread()) is executed by the
database thread?

 }
 
 void DatabaseThread::cleanupDatabaseThreadCompleted()