How can I make FPS of html5 independent of the swf loaded

I noticed something unusual, and don’t know why I did not notice this before.

I tried to set the FPS of the html5 build to 12 inside project.xml It was not working, and was very fast.
Then I added a line stage.frameRate = 12 . That too did not work, and still was very fast.
I did not understand why it was not working.
After that I opened up the Fla, and set it’s stage frame rate to 12 ( from 30 ).
This time it worked.

So it seems that the html5 build takes the fps from the swf being used. How can I make it independent of it’s fps ?