Add UseCounter entry for SVGForeignObjectElement

Add UseCounter entry for SVGForeignObjectElement

There have been discussions about removing foreignObject and instead
allow an html element with position and dimensions inside svg. Knowing
how popular foreignObject is may be useful in such discussions.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170561

[davve, 2014-04-01 11:18:21]

I see that there is some considerable skew in how the SVGSVGElement counter
compares to SVGSVGElementInDocument. Do you think we need to do the
corresponding for foreignObject? 

Personally, I don't think libraries are creating foreignObject for testing in
the same extent as they do for svg:svg so perhaps this simpler way is enough.
What do you think?

[Stephen Chennney, 2014-04-01 12:05:57]

lgtm

I agree that we do not need to be very concerned about object creation to check
for support. The Stack Overflow thread that ed commented on indicates that you
can't test by trying to create the object.

[commit-bot: I haz the power, 2014-04-01 12:05:59]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/davve@opera.com/220713003/1

[commit-bot: I haz the power, 2014-04-01 13:14:56]

Change committed as 170561