Support larger bitmaps in BitmapFactory.Options.inBitmap

bug:8121994

Adds a new distiction between bitmap size and the allocation
(pixel ref/buffer) used to store its data.

BitmapFactory.inBitmap will allow a bitmap to be reinitialized with
new data if the bitmap being decoded is (after sampleSize) equal or
smaller.

Change-Id: I747750a735c858882df3af74fca6cdc46f2a9f81