1. Sometimes unlocking the device when the IME is up and triple tapping on the keyboard
toggles screen magnification. The core reason is that when the kayguard window is
shown we hide all other windows and when it is hidden we show these windows. We did
not notify the screen magnifier for windows being shown and hidden. Also when the
windows are shown we may reassign layers to put the IME or the wallpaper in the
right Z order. The screen magnifier is now notified upon such layer reassignment
since window layers are used when computing the magnified region.
bug:7351531
Change-Id: I0931f4ba6cfa565d8eb1e3c432268ba1818feea6
55468c64bc