Fixed incorrect calculation of dirty invalidation area

Padding was already taken into consideration before calling
invalidateDrawable in ProgressBar.

Change-Id: I75f25b0b7ee87d394422c58888ed3a1cca5d06a8
Avoid duplicate call to onLoadFinished()

When a loader is initialized in Fragment#onActivityCreated(Bundle), then
LoadersCallback#onLoadFinished() was called twice on device orientation
change:
 - once during fragment start();
 - once during loader finishRetain().

Reported as bug 63179:
https://code.google.com/p/android/issues/detail?id=63179

This commit prevents to call onLoadFinished() when the data has already
been delivered.

Change-Id: I893013049f819dd5543a8079ce9d8025a5fdb2f1
Out of memory using wallpaperPicker switching wallpapers

Out of memory issues arise when switching wallpapers using
WallpaperPicker quickly, due to not releasing large Bitmaps
before allocating space for new ones.

Resolved by securing that wallpaper bitmaps are set to null
in order to be garbage collected when switching wallpaper.

Added stability correction making sure noone can retrieve
bitmap once it has been recycled by first calling
WallpaperManager.forgetLoadedWallpaper().

Change-Id: I318ee46d8613bec15dd52dd7b61ae950e760e6f6