If the dimensions of the original are sufficiently different from the
device's preferred dimensions, just don't restore the image. This
avoids bad letterboxing / clipping on e.g. phone <-> tablet data
migration.
The expansion/shrinkage ratios used here allow restores of saved
wallpaper images among HVGA devices, among WVGA variants, and
among tablets; but skip restoring wallpapers across those
categories (where severe clipping or letterboxing would occur).
Bug 3261863
Change-Id: I75e75d6401d18f1df10d75796ee04e21d2302cfa
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.
