Generalize change transition into WindowContainer

Created a SurfaceFreezer class which lives in WindowContainer
and manages/will-manage per-container freezing (snapshots).
This replaces the one-off change transition code.

Change Transitions used to create its own temporary leash
on initialization and that leash would be replaced/cleaned-up
as soon as the animation leash was created.

Now, the SurfaceFreezer creates the animation leash immediately
and SurfaceAnimator can take a SurfaceFreezer instance when it
starts an animation. At this point it will take the leash that
was already created by the freezer and use that. This removes
the messy reparenting/cleanup.

To deal with this, though, leash callbacks into Animatable
needed an extra stage: onLeashAnimationStarting. This is called
when SurfaceAnimatior is actually starting to animate the leash.

Next, DC.mChangingApps was converted to list of WindowContainers
rather than ActivityRecords. Some of the existing change code was
cleaned up (ie. there was some visibility stuff that doesn't make
sense because changing apps are visible->visible) and some of the
Activity-specific functions were generalized. For now, there are
a couple things that use the top-activity for changing Tasks.

The result of this means that windowing-mode change transition can
now fully live at the Task level. This also should allow freezing
at any hierarchy level which enables app-freezes that don't freeze
the whole screen and potentially mixed seamless/snapshot-based
rotations.

Bug: 149490428
Test: existing tests pass. Manually open app in freeform and
      maximize/restore it.
Change-Id: Ib32524ebbbb084a98442d3d035897306a11ee6c2
(cherry picked from commit e55b9e0f9d0377af313591d9e0c260d41c7fe3d1)

0 files changed, 0 insertions, 0 deletions