Fix bug where setting canvas size to 0 was treated as if context was lost

Fix bug where setting canvas size to 0 was treated as if context was lost

The canvas context lost handling logic was falsely kicking, rendering
the canvas unusable when setting one of its dimensions to zero.

BUG=532148
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=202645

[Justin Novosad, 2015-09-16 19:43:07]

junov@chromium.org changed reviewers:
+ senorblanco@chromium.org

[Justin Novosad, 2015-09-16 19:43:08]

PTAL

[Stephen White, 2015-09-16 19:50:20]

LGTM

[Justin Novosad, 2015-09-16 19:59:41]

The CQ bit was checked by junov@chromium.org

[commit-bot: I haz the power, 2015-09-16 20:00:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1350883002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1350883002/1

[commit-bot: I haz the power, 2015-09-16 20:48:59]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-09-16 20:48:59]

Try jobs failed on following builders:
  linux_chromium_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Justin Novosad, 2015-09-22 18:22:43]

The CQ bit was checked by junov@chromium.org

[Justin Novosad, 2015-09-22 18:22:44]

The patchset sent to the CQ was uploaded after l-g-t-m from
senorblanco@chromium.org
Link to the patchset: https://codereview.chromium.org/1350883002/#ps20001
(title: "fix layout test")

[commit-bot: I haz the power, 2015-09-22 18:23:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1350883002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1350883002/20001

[commit-bot: I haz the power, 2015-09-22 21:06:09]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=202645