Fixes for JPEG subset decoding.

Fixes for JPEG subset decoding.

Ensure that the stream passed to JPEG for subset decoding is
neither deleted before it is no longer needed nor deleted an
extra time.

src/images/SkJpegUtility.h:
src/images/SkJpegUtility.cpp:
Always ref and unref the stream provided to skjpeg_source_mgr.
Add some comments explaining how skjpeg_source_mgr's members
handle ownership.
Fix a warning comparing signed and unsigned numbers, converting
to size_t which is more appropriate for measuring bytes.
Remove dead code referring to fMemoryBase and fMemoryBaseSize,
which are never used.

src/images/SkImageDecoder_libjpeg.cpp:
Call the new constructor for skjpeg_source_mgr, which no longer
takes a boolean to determine ownership.

include/images/SkBitmapRegionDecoder.h
src/images/SkBitmapRegionDecoder.cpp:
This small shim has been removed, since it is not needed to use
Skia's image decoders. Its functionality will be folded into
Android.

Required for the merge to Android.

R=djsollen@google.com

Committed: https://code.google.com/p/skia/source/detail?r=10483

[djsollen, 2013-08-01 14:41:33]

lgtm

[scroggo, 2013-08-01 15:02:40]

new patch removes reference to *deleted* file from the gyp.

[djsollen, 2013-08-01 15:03:14]

lgtm

[scroggo, 2013-08-01 15:03:46]

Committed patchset #2 manually as r10483 (presubmit successful).