This fixes a bunch of edge cases in updating the wallpaper's scroll position
and visibility when switching between wallpapers and traveling through the UI.
It also fixes some leaks of wallpaper tokens and windows.
- Do better about figuring out when to stop them and other related window
management.
- Fix problem where we were not redrawing the surface when the orientation
changed. This was the cause of the device hang.
- Recover if a live wallpaper is crashing repeatedly.
- Don't crash when someone tries to set a static wallpaper.
- Make the static wallpaper update correctly when the image changes.
This is all of the basic pieces:
- The WallpaperService now creates a surface with the window manager for its
contents.
- There is a simple service that displays a bitmap.
- The wallpaper manager takes care of starting and stopping the service.
- The window manager knows about wallpaper windows and how to layer them with
the windows that want to be shown on top of wallpaper.
Lots and lots of issues remain, but at this point you can actually write a
wallpaper service, select it in the UI, and see it behind an activity.
This is mostly refactoring, adding a new WallpaperManager class that takes care
of the old wallpaper APIs on Context, so we don't need to pollute Context with
various new wallpaper APIs as they are needed. Also adds the first little
definition of a wallpaper service, which is not yet used or useful.
