Uses
MagnificationInfoChangedCallback.onFullScreenMagnificationChanged
callback method to notify magnification hange instead of
accessing the public method of AccessibilityManagerService directly.
It reduces the interaction between AccessibilityManagerService and
FullScreenMagnificationControlller.
So that MagnificationController would take responsible for handling
notifyMagnificationChange().
Bug: 218540156
Test: atest FullScreenMagnificationControllerTest,
atest FullScreenMagnificationGestureHandlerTest,
atest MagnificationControllerTest,
Change-Id: Ib9f31681e442f1700a76250a5206199bad458c84
(cherry picked from commit 3c91f067b1)
Merged-In: Ib9f31681e442f1700a76250a5206199bad458c84
c4f1973325