SkScaledBitmapSampler: fix memory overwritten

SkScaledBitmapSampler: fix memory overwritten

Memory will be overwritten while downsampling some
interlaced gif images, most commonly with odd sizes,
when index of destination row stores in the current
line computed from GifInterlaceIter meets:

 X is an integer in [0..height-1]
   and
 (X < height)
 && ((X - sampleSize/2) % sampleSize == 0)
 && ((X - sampleSize/2)/sampleSize >= height/sampleSize)

Signed-off-by: Lu Tong <lu.x.tong@sonymobile.com>;

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/9c798207b7c710148d7f2989e877a7ece62edd5e

[Zoran Jovanovic, 2015-04-15 10:41:48]

zoran.jovanovic@sonymobile.com changed reviewers:
+ scroggo@google.com, tomhudson@chromium.org

[Zoran Jovanovic, 2015-04-15 10:46:01]

zoran.jovanovic@sonymobile.com changed reviewers:
+ reed@android.com

[scroggo, 2015-04-15 12:02:01]

On 2015/04/15 10:46:29, Zoran Jovanovic wrote:

The code looks good. Do you have a sample image/samplesize that can be used to
test?

[Zoran Jovanovic, 2015-04-15 12:13:30]

On 2015/04/15 12:02:01, scroggo wrote:
> On 2015/04/15 10:46:29, Zoran Jovanovic wrote:
> 
> The code looks good. Do you have a sample image/samplesize that can be used to
> test?

Sending in separate email (can you add attachments in Rietveld?).

[scroggo, 2015-04-16 17:45:24]

On 2015/04/15 12:13:30, Zoran Jovanovic wrote:
> On 2015/04/15 12:02:01, scroggo wrote:
> > On 2015/04/15 10:46:29, Zoran Jovanovic wrote:
> > 
> > The code looks good. Do you have a sample image/samplesize that can be used
to
> > test?
> 
> Sending in separate email (can you add attachments in Rietveld?).

I am not aware of the ability to add attachments in Rietveld. I've received the
image and confirmed that we crash without this fix, and pass with it.

I would like to add a test, but we need to have an image whose copyright (or
lack thereof) allows us to check it into resources. Since I do not want that to
hold this up, I'll approve this now.

LGTM.

I've written a test at https://codereview.chromium.org/1091053002, which we can
check in once we have an image to test with. (I was going to file a bug, but our
bug db is read-only for maintenance.)

[scroggo, 2015-04-16 17:45:28]

The CQ bit was checked by scroggo@google.com

[commit-bot: I haz the power, 2015-04-16 17:45:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1085253002/1

[commit-bot: I haz the power, 2015-04-16 18:03:19]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/9c798207b7c710148d7f2989e877a7ece62edd5e