Fix SkClipStack bug with inverse-filled difference elements

Fix SkClipStack bug with inverse-filled difference elements

Previously, SkClipStack would call "setEmpty" on itself when an
inverse-filled difference element made the stack empty. This was
a problem because setEmpty would forget the element had an inverse
fill, yet leave the op as "difference". This change modifies it to
manually update the clip bounds and set the gen-ID to kEmptyGenID,
rather than calling setEmpty.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2175493002

Committed: https://skia.googlesource.com/skia/+/d50e2401787dc5632453293b65f8255b12450b9b

[csmartdalton, 2016-07-22 00:10:08]

Description was changed from

==========
Fix SkClipStack bug with inverse-filled difference elements

Previously, SkClipStack would call "setEmpty" on itself when an
inverse-filled difference element made the stack empty. This was
a problem because setEmpty would forget the element had an inverse
fill, yet leave the op as "difference". This change updates it to
manually update the clip bounds and set the gen-ID to kEmptyGenID,
rather than calling setEmpty.

BUG=skia:
==========

to

==========
Fix SkClipStack bug with inverse-filled difference elements

Previously, SkClipStack would call "setEmpty" on itself when an
inverse-filled difference element made the stack empty. This was
a problem because setEmpty would forget the element had an inverse
fill, yet leave the op as "difference". This change updates it to
manually update the clip bounds and set the gen-ID to kEmptyGenID,
rather than calling setEmpty.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2175493002
==========

[csmartdalton, 2016-07-22 00:54:58]

Description was changed from

==========
Fix SkClipStack bug with inverse-filled difference elements

Previously, SkClipStack would call "setEmpty" on itself when an
inverse-filled difference element made the stack empty. This was
a problem because setEmpty would forget the element had an inverse
fill, yet leave the op as "difference". This change updates it to
manually update the clip bounds and set the gen-ID to kEmptyGenID,
rather than calling setEmpty.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2175493002
==========

to

==========
Fix SkClipStack bug with inverse-filled difference elements

Previously, SkClipStack would call "setEmpty" on itself when an
inverse-filled difference element made the stack empty. This was
a problem because setEmpty would forget the element had an inverse
fill, yet leave the op as "difference". This change modifies it to
manually update the clip bounds and set the gen-ID to kEmptyGenID,
rather than calling setEmpty.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2175493002
==========

[csmartdalton, 2016-07-22 00:56:43]

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

[csmartdalton, 2016-07-22 00:56:43]

Hey guys, not sure if you are the right reviewers for this one, but I ran into
this bug while trying to land https://codereview.chromium.org/2160093002/.

[bsalomon, 2016-07-22 13:22:51]

lgtm

[csmartdalton, 2016-07-22 15:15:27]

The CQ bit was checked by csmartdalton@google.com

[commit-bot: I haz the power, 2016-07-22 15:15:32]

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, 2016-07-22 15:39:08]

Description was changed from

==========
Fix SkClipStack bug with inverse-filled difference elements

Previously, SkClipStack would call "setEmpty" on itself when an
inverse-filled difference element made the stack empty. This was
a problem because setEmpty would forget the element had an inverse
fill, yet leave the op as "difference". This change modifies it to
manually update the clip bounds and set the gen-ID to kEmptyGenID,
rather than calling setEmpty.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2175493002
==========

to

==========
Fix SkClipStack bug with inverse-filled difference elements

Previously, SkClipStack would call "setEmpty" on itself when an
inverse-filled difference element made the stack empty. This was
a problem because setEmpty would forget the element had an inverse
fill, yet leave the op as "difference". This change modifies it to
manually update the clip bounds and set the gen-ID to kEmptyGenID,
rather than calling setEmpty.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2175493002

Committed:
https://skia.googlesource.com/skia/+/d50e2401787dc5632453293b65f8255b12450b9b
==========

[commit-bot: I haz the power, 2016-07-22 15:39:09]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/d50e2401787dc5632453293b65f8255b12450b9b