Provide correct saveLayer() bounds in FEGaussianBlur, FEMorphology.

Provide correct saveLayer() bounds in FEGaussianBlur, FEMorphology.

In Skia r13323, I changed Skia's image filter clipping behaviour to
expand clip bounds to accommodate filter margins. However, the legacy
Blink DAG already makes such accommodation, which means we're creating
an offscreen with redundant pixels. The fix is to specify the computed
bounds directly in saveLayer(), which overrides (well, actually
intersects) the clip, giving the correct bounds. This does give
different results for large blur sigmas, but I believe the new results
are spec-correct: the intermediate buffers used by filters should
never exceed the size of the filter region.

Covered by marked svg tests.

BUG=
R=schenney@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170232

[Stephen White, 2014-03-27 17:56:00]

Florin: PTAL. Thanks!

[Stephen Chennney, 2014-03-27 18:59:31]

LGTM. You are right about the correct behavior for large std filter std
deviations.

[Stephen White, 2014-03-27 19:06:39]

The CQ bit was checked by senorblanco@chromium.org

[commit-bot: I haz the power, 2014-03-27 19:06:49]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/senorblanco@chromium.org/214693008/1

[Stephen White, 2014-03-27 19:06:55]

The CQ bit was unchecked by senorblanco@chromium.org

[Stephen White, 2014-03-27 19:08:49]

The CQ bit was checked by senorblanco@chromium.org

[commit-bot: I haz the power, 2014-03-27 19:08:54]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/senorblanco@chromium.org/214693008/20001

[Stephen White, 2014-03-27 19:47:21]

The CQ bit was checked by senorblanco@chromium.org

[commit-bot: I haz the power, 2014-03-27 19:47:24]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/senorblanco@chromium.org/214693008/40001

[commit-bot: I haz the power, 2014-03-27 20:54:15]

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

[commit-bot: I haz the power, 2014-03-27 20:54:16]

Try jobs failed on following builders:
  tryserver.blink on linux_blink_dbg

[Stephen White, 2014-03-27 20:55:39]

The CQ bit was checked by senorblanco@chromium.org

[commit-bot: I haz the power, 2014-03-27 20:55:43]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/senorblanco@chromium.org/214693008/40001

[commit-bot: I haz the power, 2014-03-27 21:17:28]

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

[commit-bot: I haz the power, 2014-03-27 21:17:29]

Try jobs failed on following builders:
  tryserver.blink on linux_blink_rel

[Stephen White, 2014-03-27 21:30:34]

The CQ bit was checked by senorblanco@chromium.org

[commit-bot: I haz the power, 2014-03-27 21:30:37]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/senorblanco@chromium.org/214693008/40001

[commit-bot: I haz the power, 2014-03-27 22:33:00]

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

[commit-bot: I haz the power, 2014-03-27 22:33:01]

Commit queue rejected this change because the description was changed
between the time the change entered the commit queue and the time it
was ready to commit. You can safely check the commit box again.

[Stephen White, 2014-03-27 23:08:36]

The CQ bit was checked by senorblanco@chromium.org

[commit-bot: I haz the power, 2014-03-27 23:08:44]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/senorblanco@chromium.org/214693008/40001

[commit-bot: I haz the power, 2014-03-28 00:15:26]

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

[commit-bot: I haz the power, 2014-03-28 00:15:26]

Try jobs failed on following builders:
  tryserver.blink on linux_blink_dbg

[Stephen White, 2014-03-28 00:53:52]

Committed patchset #3 manually as r170232 (presubmit successful).