Update VideoImageGenerator to match new API.

Update VideoImageGenerator to match new API.

SkImageGenerator is in the process of adding an enum return value to
onGetPixels. For staging, it has been replaced with onGetPixelsEnum.
(See https://codereview.chromium.org/919693002/)

Implement the new API. A follow up change will rename onGetPixelsEnum
to onGetPixels.

No need to check for null pixels; onGetPixels is only called by
getPixels which has already done the check.

R=reed@google.com,fmalita@chromium.org

BUG=skia:3257
Committed: https://crrev.com/8d58e2c4771cfee729eac8307a62c2eb6752cfa5
Cr-Commit-Position: refs/heads/master@{#317038}

[reed1, 2015-02-18 14:53:58]

skia-side lgtm

[merkulova, 2015-02-18 14:59:48]

merkulova@chromium.org changed reviewers:
- merkulova@chromium.org

[merkulova, 2015-02-18 15:01:33]

I'm completely unfamiliar with skia code, sorry. Removing myself from reviewers.

[reed1, 2015-02-18 15:03:27]

I presume we need a media/ owner...

/blink/src/media> cat OWNERS 
dalecurtis@chromium.org
ddorwin@chromium.org
jrummell@chromium.org
sandersd@chromium.org
scherkus@chromium.org
wolenetz@chromium.org
xhwang@chromium.org

[scroggo, 2015-02-18 15:04:57]

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

[scroggo, 2015-02-18 15:04:57]

Adding an OWNER. dalecurtis@, do you mind taking a look?

[DaleCurtis, 2015-02-19 01:30:35]

rs lgtm given the skia@ folk are happy.

[scroggo, 2015-02-19 12:52:14]

The CQ bit was checked by scroggo@google.com

[commit-bot: I haz the power, 2015-02-19 12:53:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/934263002/1

[commit-bot: I haz the power, 2015-02-19 14:02:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-19 14:03:42]

Patchset 1 (id:??) landed as
https://crrev.com/8d58e2c4771cfee729eac8307a62c2eb6752cfa5
Cr-Commit-Position: refs/heads/master@{#317038}