Some optimizations in blur outline generator

1) Using ALPHA_8 as the start and end bitmap. This removes one extra
   bitmap generation step
2) Using ByteBuffer on ALPHA_8 bitmap for clipAlpha. This allows us
   to use byteArray instead of intArray for representing pixels

Change-Id: I1b654c439fd491b6b91180ddc562bb97fad857aa
5 files changed