To support switching magnification mode, we add callback to know
when the animation is finished. We only invoke the newest callback
when the animation is end successfully or the spec didn't change
Bug: 161669184
Test: atest com.android.systemui.accessibility
atest com.android.server.accessibility.magnification
Enable window magnification to see if it works normally
Change-Id: I34ce39d133a000964d1089946b7bcf510a618b40
6045db95e6