Remove MediaQueryListListener.idl

MediaQueryListListener.idl is not used, and the method it contains is
no longer in the spec, which in any case is experimental:
https://developer.mozilla.org/en-US/docs/Web/API/MediaQueryListListener

The class *is* used (the .h and .cpp are used), but the .idl isn't.

Also merges a unit test into TestObject.idl (as we're not doing unit
tests for individual types).

Review URL: https://codereview.chromium.org/64093006

git-svn-id: svn://svn.chromium.org/blink/trunk@162326 bbb929c8-8fbe-4397-9dbb-9b2b20218538