Remove unused equality operator from ComputedStyleBase.

Remove unused equality operator from ComputedStyleBase.

ComputedStyleBase::operator== is generated incorrectly since it includes
nonproperty fields as well. Fortunately, the equality operator is never
called anywhere, so it didn't cause any issues. This patch removes this
operator so that we don't accidentally use it in the future.

ComputedStyle has a correct equality implementation that should be used
instead.

BUG=628043
Review-Url: https://codereview.chromium.org/2736563002
Cr-Commit-Position: refs/heads/master@{#455606}
Committed: https://chromium.googlesource.com/chromium/src/+/483a632594b00e8cbaa061aeb86c9f9fd965e2ba

[shend, 2017-03-07 01:26:06]

The CQ bit was checked by shend@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-07 01:26:37]

Dry run: 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, 2017-03-07 04:27:44]

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

[commit-bot: I haz the power, 2017-03-07 04:27:45]

Dry run: Try jobs failed on following builders:
  win_chromium_x64_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[shend, 2017-03-07 06:08:33]

shend@chromium.org changed reviewers:
+ meade@chromium.org

[shend, 2017-03-07 06:08:34]

Hi Eddy, PTAL :)

[meade_UTC10, 2017-03-07 23:12:13]

lgtm

[shend, 2017-03-08 23:04:43]

The CQ bit was checked by shend@chromium.org

[commit-bot: I haz the power, 2017-03-08 23:05:42]

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, 2017-03-09 00:16:58]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1489014283572480, "parent_rev":
"9d0fedea76764c9132e6d19ec8679880339a8eef", "commit_rev":
"483a632594b00e8cbaa061aeb86c9f9fd965e2ba"}

[commit-bot: I haz the power, 2017-03-09 00:17:39]

Description was changed from

==========
Remove unused equality operator from ComputedStyleBase.

ComputedStyleBase::operator== is generated incorrectly since it includes
nonproperty fields as well. Fortunately, the equality operator is never
called anywhere, so it didn't cause any issues. This patch removes this
operator so that we don't accidentally use it in the future.

ComputedStyle has a correct equality implementation that should be used
instead.

BUG=628043
==========

to

==========
Remove unused equality operator from ComputedStyleBase.

ComputedStyleBase::operator== is generated incorrectly since it includes
nonproperty fields as well. Fortunately, the equality operator is never
called anywhere, so it didn't cause any issues. This patch removes this
operator so that we don't accidentally use it in the future.

ComputedStyle has a correct equality implementation that should be used
instead.

BUG=628043

Review-Url: https://codereview.chromium.org/2736563002
Cr-Commit-Position: refs/heads/master@{#455606}
Committed:
https://chromium.googlesource.com/chromium/src/+/483a632594b00e8cbaa061aeb86c...
==========

[commit-bot: I haz the power, 2017-03-09 00:17:40]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/483a632594b00e8cbaa061aeb86c...

[sashab, 2017-03-09 00:21:02]

sashab@chromium.org changed reviewers:
+ sashab@chromium.org

[sashab, 2017-03-09 00:21:02]

Hold on, this patch not LGTM.

Eventually ComputedStyle will go away, so we want ComputedStyleBase to have the
correct equality implementation for when that happens.

What we should be doing instead, if we want to keep operator==, is:

ComputedStyleBase::operator==(other) {
      ... generated fields ...
}

ComputedStyle::operator==(other) {
    return ComputedStyleBase::operator==(other) &&
      ... existing nongenerated fields ...
}

Otherwise, when the fields in the existing equality operator become generated,
the behavior will be inconsistent.

[shend, 2017-03-09 02:47:44]

On 2017/03/09 at 00:21:02, sashab wrote:
> Hold on, this patch not LGTM.
> 
> Eventually ComputedStyle will go away, so we want ComputedStyleBase to have
the correct equality implementation for when that happens.
> 
> What we should be doing instead, if we want to keep operator==, is:
> 
> ComputedStyleBase::operator==(other) {
>       ... generated fields ...
> }
> 
> ComputedStyle::operator==(other) {
>     return ComputedStyleBase::operator==(other) &&
>       ... existing nongenerated fields ...
> }
> 
> Otherwise, when the fields in the existing equality operator become generated,
the behavior will be inconsistent.

After some offline discussion, we agreed that the current implementation of
ComputedStyle::operator== is misleading since some fields are excluded in the
comparison. I'll add a TODO in a separate patch to change ::operator== to a
named method (like nonInheritedEquals) that better describes what it's doing.