Fix an assert statement in SkPngCodec

Fix an assert statement in SkPngCodec

allRowsCallback was asserting that
    rowNum - fFirstRow == fLinesDecoded

But it was expecting fFirstRow to be 0 (logically, it is, since we are
decoding all rows), and it never set it (because it doesn't really need
to, except for this assert). This is only a problem if we reuse an
SkPngCodec after previously scaling with it. Add a test that triggers
the assert, and fix it.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2401133002

Committed: https://skia.googlesource.com/skia/+/c46cdd48eb0d04f54ecad8ecfa7b3158090c3a0a

[scroggo_chromium, 2016-10-07 20:29:07]

Description was changed from

==========
Fix an assert statement in SkPngCodec

allRowsCallback was asserting that
    rowNum - fFirstRow == fLinesDecoded

But it was expecting fFirstRow to be 0 (logically, it is, since we are
decoding all rows), and it never set it (because it doesn't really need
to, except for this assert). This is only a problem if we reuse an
SkPngCodec after previously scaling with it. Add a test that triggers
the assert, and fix it.
==========

to

==========
Fix an assert statement in SkPngCodec

allRowsCallback was asserting that
    rowNum - fFirstRow == fLinesDecoded

But it was expecting fFirstRow to be 0 (logically, it is, since we are
decoding all rows), and it never set it (because it doesn't really need
to, except for this assert). This is only a problem if we reuse an
SkPngCodec after previously scaling with it. Add a test that triggers
the assert, and fix it.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2401133002
==========

[scroggo_chromium, 2016-10-07 20:29:40]

scroggo@chromium.org changed reviewers:
+ msarett@google.com

[msarett, 2016-10-10 00:32:18]

Should we be reseting this field in onRewind()?

lgtm

[scroggo_chromium, 2016-10-10 13:21:42]

On 2016/10/10 00:32:18, msarett wrote:
> Should we be reseting this field in onRewind()?

I think onRewind is the wrong place for it. The other versions set it in
decodeAllRows, so I set it there for consistency.

> 
> lgtm

[scroggo_chromium, 2016-10-10 13:21:47]

The CQ bit was checked by scroggo@chromium.org

[scroggo_chromium, 2016-10-10 13:21:47]

The patchset sent to the CQ was uploaded after l-g-t-m from msarett@google.com
Link to the patchset: https://codereview.chromium.org/2401133002/#ps40001
(title: "Set fFirstRow and fLastRow")

[commit-bot: I haz the power, 2016-10-10 13:21:53]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-10-10 13:45:34]

Description was changed from

==========
Fix an assert statement in SkPngCodec

allRowsCallback was asserting that
    rowNum - fFirstRow == fLinesDecoded

But it was expecting fFirstRow to be 0 (logically, it is, since we are
decoding all rows), and it never set it (because it doesn't really need
to, except for this assert). This is only a problem if we reuse an
SkPngCodec after previously scaling with it. Add a test that triggers
the assert, and fix it.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2401133002
==========

to

==========
Fix an assert statement in SkPngCodec

allRowsCallback was asserting that
    rowNum - fFirstRow == fLinesDecoded

But it was expecting fFirstRow to be 0 (logically, it is, since we are
decoding all rows), and it never set it (because it doesn't really need
to, except for this assert). This is only a problem if we reuse an
SkPngCodec after previously scaling with it. Add a test that triggers
the assert, and fix it.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2401133002

Committed:
https://skia.googlesource.com/skia/+/c46cdd48eb0d04f54ecad8ecfa7b3158090c3a0a
==========

[commit-bot: I haz the power, 2016-10-10 13:45:35]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/c46cdd48eb0d04f54ecad8ecfa7b3158090c3a0a