Remove SK_OFFSETOF from SkTypes, clean up offsetof usage.

Remove SK_OFFSETOF from SkTypes, clean up offsetof usage.

The motivation for this was to remove SK_OFFSETOF from SkTypes, but
this CL is mostly about cleaning up our use of offsetof generally.

SK_OFFSETOF is removed to SkTypes and added to the two places it is
actually used (for the non standard behavior of finding the offset of
fields in types which are not standard layout).

Older versions of gcc required POD for offsetof to be used without
warning. Newer versions require the more relaxed standard layout.
Now that we no longer build on older versions of gcc, remove the
old warning suppressions.

PODMatrix is renamed to AggregateMatrix. SkMatrix is already POD
(trivial and standard layout). The PODMatrix name implies that the
POD-ness is needed for the offsetof, but it is actually the aggregate
attribute which is needed for compile time constant initialization.
This makes it more obvious that this can be revisited after we can
rely on constexpr constructors.

This also adds skstd::declval since this allows removal of existing
awkward code which casts a constant to a pointer to find the size of
a field.

TBR=reed@google.com
No API change, only removes unused macro.

Committed: https://skia.googlesource.com/skia/+/afd7c749724ccceb88761c52c196ba371be5fb1c

[bungeman-skia, 2015-08-25 17:59:19]

bungeman@google.com changed reviewers:
+ mtklein@google.com

[bungeman-skia, 2015-08-25 17:59:44]

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

[commit-bot: I haz the power, 2015-08-25 17:59:54]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1309523003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1309523003/1

[mtklein, 2015-08-25 18:04:36]

lgtm

https://codereview.chromium.org/1309523003/diff/1/src/core/SkMatrix.cpp
File src/core/SkMatrix.cpp (right):

https://codereview.chromium.org/1309523003/diff/1/src/core/SkMatrix.cpp#newco...
src/core/SkMatrix.cpp:1589: // SkMatrix is C++11 POD (trivial and
standard-layout), but not aggragate (it has private fields).
sp. on aggregate

[bungeman-skia, 2015-08-25 18:07:15]

https://codereview.chromium.org/1309523003/diff/1/src/core/SkMatrix.cpp
File src/core/SkMatrix.cpp (right):

https://codereview.chromium.org/1309523003/diff/1/src/core/SkMatrix.cpp#newco...
src/core/SkMatrix.cpp:1589: // SkMatrix is C++11 POD (trivial and
standard-layout), but not aggragate (it has private fields).
On 2015/08/25 18:04:36, mtklein wrote:
> sp. on aggregate

Done.

[bungeman-skia, 2015-08-25 18:07:28]

The CQ bit was checked by bungeman@google.com

[bungeman-skia, 2015-08-25 18:07:28]

The patchset sent to the CQ was uploaded after l-g-t-m from mtklein@google.com
Link to the patchset: https://codereview.chromium.org/1309523003/#ps20001
(title: "Speling")

[commit-bot: I haz the power, 2015-08-25 18:07:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1309523003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1309523003/20001

[commit-bot: I haz the power, 2015-08-25 19:05:58]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/afd7c749724ccceb88761c52c196ba371be5fb1c