Revert of Scanline decoding for gifs (patchset #15 id:380001 of https://codereview.chromium.org/1305123002/ )

Reason for revert:
Breaks the build with SkScanlineDecoder.h not found:

http://build.chromium.org/p/client.skia/builders/Linux%20Builder/builds/3722/steps/compile/logs/stdio

../../third_party/skia/src/utils/SkBitmapRegionCanvas.h:10:10: fatal error: 'SkScanlineDecoder.h' file not found
#include "SkScanlineDecoder.h"

Original issue's description:
> Scanline decoding for gifs
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/e9c10b9121887e8c300bd41357461418e061984d

TBR=scroggo@google.com,djsollen@google.com,msarett@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1320273004
7 files changed