Split out whether frame callback and tick is scheduled

Since the animation/gesture for screen zoom is running at
vsync-app, calling WMS.scheduleAnimation will schedule only
at the next frame. However, in the next frame, only the frame
callback is handled but not the tick yet, however
mAnimationScheduled was still true. Thus, the request to schedule
another frame callback is ignored, and then the things get
updated only every 2nd frame.

Fix this by splitting the information whether the frame callback
is scheduled or the actual tick.

Test: Use accessibility screen zoom, make sure gestures are
smooth.
Fixes: 37476440

Change-Id: I2301fab5bf3f3b896d4aa131fb041b89572fa3a7