Analyze between two arbitrary points irrespective of thread-id

[harendra-kumar]

Currently we treat a window specific to a thread, the same thread starts and closes a window. In general, we can allow any thread to open a window and any other thread to close it. As long as we know that the window is not concurrently used by multiple threads we can use successive START and END markers as start and end of the window irrespective of which thread logged it.