Skip caching in all scopes

Skip caching in all scopes

It's hard to match scoped display items to cached display items because
sometimes the scope id is not stable (such as collapsed border paintings
in a table).

Because scopes are rare (currently used for table collapsed borders,
printing, reflection and multi-column), we expect this won't affect
performance of most normal web pages.

If this looks good, we could also remove scopeOwner, scopeId and the
logics to manage them.

BUG=500034, 497614
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197086

[Xianzhu, 2015-06-13 02:01:06]

wangxianzhu@chromium.org changed reviewers:
+ chrishtr@chromium.org

[pdr., 2015-06-13 02:55:08]

On 2015/06/13 at 02:01:07, wangxianzhu wrote:
> 

If we can't cache display items within scopes, why use scopes at all?

[Xianzhu, 2015-06-13 03:18:22]

On 2015/06/13 02:55:08, pdr wrote:
> On 2015/06/13 at 02:01:07, wangxianzhu wrote:
> > 
> 
> If we can't cache display items within scopes, why use scopes at all?

I'd like to to fully remove scope if we accept no caching of them. wdyt?

[pdr., 2015-06-13 03:51:36]

On 2015/06/13 at 03:18:22, wangxianzhu wrote:
> On 2015/06/13 02:55:08, pdr wrote:
> > On 2015/06/13 at 02:01:07, wangxianzhu wrote:
> > > 
> > 
> > If we can't cache display items within scopes, why use scopes at all?
> 
> I'd like to to fully remove scope if we accept no caching of them. wdyt?

I think this is a good idea. Scopes add significant complexity for how often
they are used, and a simpler merge algorithm will be an asset in the long run.

[chrishtr, 2015-06-13 04:44:32]

The CQ bit was checked by chrishtr@chromium.org

[chrishtr, 2015-06-13 04:44:33]

lgtm

I agree that we should consider getting rid of scopes if all goes well. Let's
commit this patch and see if any performance issues come up.

https://codereview.chromium.org/1185913002/diff/1/Source/core/paint/Deprecate...
File Source/core/paint/DeprecatedPaintLayerPainter.cpp (left):

https://codereview.chromium.org/1185913002/diff/1/Source/core/paint/Deprecate...
Source/core/paint/DeprecatedPaintLayerPainter.cpp:104: DisplayItemCacheSkipper
skipper(*context);
You can delete this class now.

[commit-bot: I haz the power, 2015-06-13 04:44:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1185913002/1

[commit-bot: I haz the power, 2015-06-13 07:18:11]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197086