Make MediaQueryList an ActiveDOMElement

Make MediaQueryList an ActiveDOMElement

This ensures that we never GC a MediaQueryList that has listeners.
It looks like that already doesn't happen (perhaps due to how
MediaQueryListListener keeps references to the JS object), but
this seems safer.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=178506

[tkent, 2014-07-18 01:40:36]

lgtm

[cbiesinger, 2014-07-18 23:14:08]

Turns out the oilpan bots were failing because I did not know that I need to add
ActiveDOMObject to the IDL file. This is now fixed, and I will add this to the
commit queue. Thanks for the lgtm.

(That's a really subtle failure though! I wonder if we can somehow detect this
better?)

[cbiesinger, 2014-07-18 23:14:15]

The CQ bit was checked by cbiesinger@chromium.org

[commit-bot: I haz the power, 2014-07-18 23:14:47]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/cbiesinger@chromium.org/397403002/40001

[commit-bot: I haz the power, 2014-07-19 00:38:13]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/17829)

[commit-bot: I haz the power, 2014-07-19 01:26:34]

Change committed as 178506