Fix GPU-only snapping bug in mask blur rendering

Fix GPU-only snapping bug in mask blur rendering

The existing mask effect code in Ganesh is subject to snapping issues (when the created mask is redrawn). This artifact can be seen by rendering the original geometry (w/o blurs) and comparing that result to a rendering of the unblurred masks. W/o this patch the results do not match up (they are arbitrarily shifted by a pixel).

This patch will require rebaselining and suppressions.

Chromium layout tests suppressions are here:
https://codereview.chromium.org/1342683003/ (Add layout test suppressions for upcoming Skia roll)

Committed: https://skia.googlesource.com/skia/+/3833daaa663db7e655a8077cdab42cca19d3a276

[robertphillips, 2015-09-13 17:50:33]

robertphillips@google.com changed reviewers:
+ bsalomon@google.com

[bsalomon, 2015-09-14 13:33:39]

lgtm, does this fix the issue you showed me the other day with the circle blur?

[robertphillips, 2015-09-14 13:38:01]

On 2015/09/14 13:33:39, bsalomon wrote:
> lgtm, does this fix the issue you showed me the other day with the circle
blur?

To paraphrase an offline conversation. This patch:

makes GPU match raster for the blurcircles GM
makes the new analytic circle blur match the old 2-pass method

[robertphillips, 2015-09-14 13:38:07]

The CQ bit was checked by robertphillips@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-09-14 13:38:17]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1338183002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1338183002/1

[commit-bot: I haz the power, 2015-09-14 13:38:57]

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

[commit-bot: I haz the power, 2015-09-14 13:38:57]

Dry run: Try jobs failed on following builders:
  Build-Ubuntu-GCC-Arm64-Debug-Android-Trybot on client.skia.compile
(JOB_FAILED,
http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu-GCC-Arm...)
  Build-Ubuntu-GCC-Mips-Debug-Android-Trybot on client.skia.compile (JOB_FAILED,
http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu-GCC-Mip...)
  Build-Ubuntu-GCC-x86_64-Release-Trybot on client.skia.compile (JOB_FAILED,
http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu-GCC-x86...)

[robertphillips, 2015-09-14 15:12:05]

The CQ bit was checked by robertphillips@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-09-14 15:12:12]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1338183002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1338183002/20001

[commit-bot: I haz the power, 2015-09-14 15:17:51]

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

[commit-bot: I haz the power, 2015-09-14 15:17:52]

Dry run: This issue passed the CQ dry run.

[robertphillips, 2015-09-14 18:17:13]

The CQ bit was checked by robertphillips@google.com

[robertphillips, 2015-09-14 18:17:13]

The patchset sent to the CQ was uploaded after l-g-t-m from bsalomon@google.com
Link to the patchset: https://codereview.chromium.org/1338183002/#ps20001
(title: "Fixed compiler complaint")

[commit-bot: I haz the power, 2015-09-14 18:17:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1338183002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1338183002/20001

[commit-bot: I haz the power, 2015-09-14 18:18:16]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/3833daaa663db7e655a8077cdab42cca19d3a276