Change MagnificationGestureHandler based on the magnificaotion mode

When the magnification mode is changed, create the correspoding
MagnificationGestureHandler based on the magnification mode and
replace it with the old one.

Bug: 152578960
Test: AccessibilityUserStateTest
Test: AccessibilityInputFilterTest
Change-Id: Ifbcb771762b660183235292d3d35de3213064573