Revert "Cache set wallpaper as PNG instead of JPEG"

Revert submission 14802973

Reason for revert: Droid cop: Possible culprits for Bug 190325415
Reverted Changes:
Ifc451f540:Cache set wallpaper as PNG instead of JPEG
Ifefd3e56d:Only rescale wallpaper if its > display height

Change-Id: I659f228ed54d09bdc950788adaf762e419dc3160

services/core/java/com/android/server/wallpaper/WallpaperManagerService.java

@@ -752,7 +752,7 @@ public class WallpaperManagerService extends IWallpaperManager.Stub
 
                         f = new FileOutputStream(wallpaper.cropFile);
                         bos = new BufferedOutputStream(f, 32*1024);
-                        finalCrop.compress(Bitmap.CompressFormat.PNG, 100, bos);
+                        finalCrop.compress(Bitmap.CompressFormat.JPEG, 100, bos);
                         bos.flush();  // don't rely on the implicit flush-at-close when noting success
                         success = true;
                     }