Merge \"Don\'t show the shade background for heads up notifications\" into nyc-dev

            float newYTranslation = state.yTranslation;

            float newHeight = state.height;

            float newNotificationEnd = newYTranslation + newHeight;

            if (newYTranslation < previousNotificationEnd) {

            boolean isHeadsUp = (child instanceof ExpandableNotificationRow)

                    && ((ExpandableNotificationRow) child).isPinned();

            if (newYTranslation < previousNotificationEnd && ambientState.isShadeExpanded()

                    && !isHeadsUp) {

                // The previous view is overlapping on top, clip!

                float overlapAmount = previousNotificationEnd - newYTranslation;

                state.clipTopAmount = (int) overlapAmount;