PIT : Modal frame hangs for a while for few seconds in 6u12 b01 pit build

I have a frame which contains a button , when i press the space bar , another frame is displayed as the first frame acts a modal frame for the second. this chain goes on until you stop creating the new window. When all the frames are visible, i click on each frame from the newly created frame to the first frame. Then for a while the whole set of frame hangs.

Step to reproduced:-
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1) Run testcase in the CR.
2) Keeping on pressing space bar . Once you see 16 frame. stop it.
3) Click each frame from low order to upper order i,e frame 15, frame14 , frame3...frame1.
4) Observe that frame16 focus border is not drawn correctly. at least the upper part. 5) Now press escape key 4 to 5 times. You will see that different frame are not painted correctly or seen above the other.

I tested this with 6u12 b01 pit build.