[qtmozembed] Drop unused attribute from QuickMozView
[qtmozembed] Don't update size of inactive views

Updating size of an inactive view doesn't make sense as its APZC won't
be notified about geometry changes anyway. But it's important to update
view's size when it gets active in order to make sure its APZC receives
up to date metrics.
Merge pull request #82 from rojkov/jb21186

Update size of active view only