Add DataPersistent<> for copy-on-modify and use for StyleFilterData.

Add DataPersistent<> for copy-on-modify and use for StyleFilterData.

Emulate what DataRef<T> provides over ref-counted objects, but
for persistent heap references. DataPersistent<T> values can
be freely copied, but when access()ed before being mutated,
DataPersistent<> ensures that the mutation will happen on
an unshared copy of the underlying heap object (of type T.)

The motivation for doing is to migrate the StyleFilterData fields
that StyleRareNonInheritedData keeps over to use DataPersistent<>
rather than DataRef<>. By doing so, StyleFilterData becomes
a simple GCed object without any ref-counting extras.

R=
BUG=604481
Committed: https://crrev.com/e5f18f7973b22a5a35fab927e2af848917e4827b
Cr-Commit-Position: refs/heads/master@{#389400}

[sof, 2016-04-21 12:55:37]

Description was changed from

==========
Add DataPersistent<> for copy-on-modify.

R=
BUG=
==========

to

==========
Add DataPersistent<> for copy-on-modify.

R=
BUG=604481
==========

[sof, 2016-04-21 12:56:19]

sigbjornf@opera.com changed reviewers:
+ oilpan-reviews@chromium.org

[sof, 2016-04-21 12:56:19]

not sure.. worth pursuing?

[haraken, 2016-04-21 13:17:13]

LGTM

[sof, 2016-04-22 13:12:47]

Description was changed from

==========
Add DataPersistent<> for copy-on-modify.

R=
BUG=604481
==========

to

==========
Add DataPersistent<> for copy-on-modify and use for StyleFilterData.

Emulate what DataRef<T> provides over ref-counted objects, but
for persistent heap references. DataPersistent<T> values can
be freely copied, but when access()ed before being mutated,
DataPersistent<> ensures that the mutation will happen on 
an unshared copy of the underlying heap object (of type T.)

The motivation for doing is to migrate the StyleFilterData fields
that StyleRareNonInheritedData keeps over to use DataPersistent<>
rather than DataRef<>. By doing so, StyleFilterData becomes
a simple GCed object without any ref-counting extras.

R=
BUG=604481
==========

[sof, 2016-04-22 14:16:31]

I'm reasonably happy with the shape of this one now, ptal?

It would have been preferable not to grow the size of StyleRareNonInheritedData
(by (sizeof(T*) + sizeof(bool)) * 2), but the StyleFilterData objects it refers
to are shrunk by no longer being  RefCountedGarbageCollected<>-derived. If
that's acceptable, then I think we're better off retiring the use of
RefCountedGarbageCollected<> for StyleFilterData (=> which in turn means that
that hybrid type can be removed altogether.)

(ftr, I'm seeing 100 - ~2k StyleRareNonInheritedData objects being created while
browsing popular web properties (e.g., gmail is < 200))

[haraken, 2016-04-22 18:07:38]

On 2016/04/22 14:16:31, sof wrote:
> I'm reasonably happy with the shape of this one now, ptal?
> 
> It would have been preferable not to grow the size of
StyleRareNonInheritedData
> (by (sizeof(T*) + sizeof(bool)) * 2), but the StyleFilterData objects it
refers
> to are shrunk by no longer being  RefCountedGarbageCollected<>-derived. If
> that's acceptable, then I think we're better off retiring the use of
> RefCountedGarbageCollected<> for StyleFilterData (=> which in turn means that
> that hybrid type can be removed altogether.)
> 
> (ftr, I'm seeing 100 - ~2k StyleRareNonInheritedData objects being created
while
> browsing popular web properties (e.g., gmail is < 200))

Yeah, it would be nice if we could remove RefCountedGarbageCollected entirely.
LGTM.

[sof, 2016-04-23 08:04:17]

On 2016/04/22 18:07:38, haraken wrote:
> On 2016/04/22 14:16:31, sof wrote:
> > I'm reasonably happy with the shape of this one now, ptal?
> > 
> > It would have been preferable not to grow the size of
> StyleRareNonInheritedData
> > (by (sizeof(T*) + sizeof(bool)) * 2), but the StyleFilterData objects it
> refers
> > to are shrunk by no longer being  RefCountedGarbageCollected<>-derived. If
> > that's acceptable, then I think we're better off retiring the use of
> > RefCountedGarbageCollected<> for StyleFilterData (=> which in turn means
that
> > that hybrid type can be removed altogether.)
> > 
> > (ftr, I'm seeing 100 - ~2k StyleRareNonInheritedData objects being created
> while
> > browsing popular web properties (e.g., gmail is < 200))
> 
> Yeah, it would be nice if we could remove RefCountedGarbageCollected entirely.
> LGTM.

I've reduced the size increase of StyleRareNonInheritedData to a pair of bools
by wrapping the persistent in an OwnPtr<>.

[haraken, 2016-04-23 18:35:10]

On 2016/04/23 08:04:17, sof wrote:
> On 2016/04/22 18:07:38, haraken wrote:
> > On 2016/04/22 14:16:31, sof wrote:
> > > I'm reasonably happy with the shape of this one now, ptal?
> > > 
> > > It would have been preferable not to grow the size of
> > StyleRareNonInheritedData
> > > (by (sizeof(T*) + sizeof(bool)) * 2), but the StyleFilterData objects it
> > refers
> > > to are shrunk by no longer being  RefCountedGarbageCollected<>-derived. If
> > > that's acceptable, then I think we're better off retiring the use of
> > > RefCountedGarbageCollected<> for StyleFilterData (=> which in turn means
> that
> > > that hybrid type can be removed altogether.)
> > > 
> > > (ftr, I'm seeing 100 - ~2k StyleRareNonInheritedData objects being created
> > while
> > > browsing popular web properties (e.g., gmail is < 200))
> > 
> > Yeah, it would be nice if we could remove RefCountedGarbageCollected
entirely.
> > LGTM.
> 
> I've reduced the size increase of StyleRareNonInheritedData to a pair of bools
> by wrapping the persistent in an OwnPtr<>.

LGTM

[sof, 2016-04-24 07:58:50]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2016-04-24 07:58:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1855213002/120001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1855213002/120001

[commit-bot: I haz the power, 2016-04-24 08:10:48]

Description was changed from

==========
Add DataPersistent<> for copy-on-modify and use for StyleFilterData.

Emulate what DataRef<T> provides over ref-counted objects, but
for persistent heap references. DataPersistent<T> values can
be freely copied, but when access()ed before being mutated,
DataPersistent<> ensures that the mutation will happen on 
an unshared copy of the underlying heap object (of type T.)

The motivation for doing is to migrate the StyleFilterData fields
that StyleRareNonInheritedData keeps over to use DataPersistent<>
rather than DataRef<>. By doing so, StyleFilterData becomes
a simple GCed object without any ref-counting extras.

R=
BUG=604481
==========

to

==========
Add DataPersistent<> for copy-on-modify and use for StyleFilterData.

Emulate what DataRef<T> provides over ref-counted objects, but
for persistent heap references. DataPersistent<T> values can
be freely copied, but when access()ed before being mutated,
DataPersistent<> ensures that the mutation will happen on 
an unshared copy of the underlying heap object (of type T.)

The motivation for doing is to migrate the StyleFilterData fields
that StyleRareNonInheritedData keeps over to use DataPersistent<>
rather than DataRef<>. By doing so, StyleFilterData becomes
a simple GCed object without any ref-counting extras.

R=
BUG=604481
==========

[commit-bot: I haz the power, 2016-04-24 08:10:49]

Committed patchset #7 (id:120001)

[commit-bot: I haz the power, 2016-04-24 08:14:31]

Description was changed from

==========
Add DataPersistent<> for copy-on-modify and use for StyleFilterData.

Emulate what DataRef<T> provides over ref-counted objects, but
for persistent heap references. DataPersistent<T> values can
be freely copied, but when access()ed before being mutated,
DataPersistent<> ensures that the mutation will happen on 
an unshared copy of the underlying heap object (of type T.)

The motivation for doing is to migrate the StyleFilterData fields
that StyleRareNonInheritedData keeps over to use DataPersistent<>
rather than DataRef<>. By doing so, StyleFilterData becomes
a simple GCed object without any ref-counting extras.

R=
BUG=604481
==========

to

==========
Add DataPersistent<> for copy-on-modify and use for StyleFilterData.

Emulate what DataRef<T> provides over ref-counted objects, but
for persistent heap references. DataPersistent<T> values can
be freely copied, but when access()ed before being mutated,
DataPersistent<> ensures that the mutation will happen on
an unshared copy of the underlying heap object (of type T.)

The motivation for doing is to migrate the StyleFilterData fields
that StyleRareNonInheritedData keeps over to use DataPersistent<>
rather than DataRef<>. By doing so, StyleFilterData becomes
a simple GCed object without any ref-counting extras.

R=
BUG=604481

Committed: https://crrev.com/e5f18f7973b22a5a35fab927e2af848917e4827b
Cr-Commit-Position: refs/heads/master@{#389400}
==========

[commit-bot: I haz the power, 2016-04-24 08:14:32]

Patchset 7 (id:??) landed as
https://crrev.com/e5f18f7973b22a5a35fab927e2af848917e4827b
Cr-Commit-Position: refs/heads/master@{#389400}