Bug 893572 - Tests. r=jmuizelaar
Bug 935624 - Kill SetZoomAndResolution because the APZC should not touch the mResolution or mCumulativeResolution. r=botond
Bug 935624 - Update various properties on the FrameMetrics on a layers update. r=botond

In particular, in the case with nested APZCs, the parent APZC might request
a repaint at a different resolution, and the child APZC might only find out
about it when the call to NotifyLayersUpdated comes in. At this point the
child APZC must pick up the new values of various properties in order to
remain consistent with the state in gecko and the parent APZC