SelectorChecker should update scope and behaviorAtBoundary for /content/ in SharingRules mode

SelectorChecker should update scope and behaviorAtBoundary for /content/ in SharingRules mode.

When ShardStyleFinder checks whether a given element can reuse other element's style
or not, it uses SelectorChecker with SharingRules mode.
However, RuleFeatureSet used in SharingRules mode doesn't have any information about styles' scope, i.e. SelectorCheckingContext's scope.
So Blink should treat as if scope and behavior are set correctly.

BUG=353428
TEST=fast/dom/shadow/style-sharing-with-content-and-host.html

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170176

[tasak, 2014-03-19 08:05:52]

Would you review this CL?

[esprehn, 2014-03-19 08:12:07]

Can you explain this in more detail? I feel like the behaviorAtBoundary values
are not very well understood except for you. :)

[tasak, 2014-03-25 10:56:25]

On 2014/03/19 08:12:07, esprehn wrote:
> Can you explain this in more detail? I feel like the behaviorAtBoundary values
> are not very well understood except for you. :)

Sure.

behaviorAtBoundary explains how context.scope works.

If behaviorAtBoundary is:
(a) ScopeIsShadowHost, the context.scope works as shadow host. So context.scope
is in shadow trees hosted by the context.scope.

(b) StayWithinTreescope, SelectorChecker has two scope. One is context.scope and
the other is treescope. context.scope is used for :scope, e.g.
element.querySelector(":host :scope div").

(c) Otherwise, the context.scope should be a scoping node of a style scoped.

In (b) and (c) case, context.scope is not a root of shadow trees.

(a) and (c) is used for styleForElement (ResolvingStyle mode or CollectingRules
mode). (b) is used for querySelector or sharedStyleFinder (SharingRules or
QueryingRules mode).

So, when sharedStyleFinder wants to check whether some element can reuse an
existing style used by another element or not,
basically context.scope is not required except :host and :scope.

:host and :scope depends on where a rule is declared (=context.scope
information).

[esprehn, 2014-03-27 13:22:02]

On 2014/03/25 at 10:56:25, tasak wrote:
> On 2014/03/19 08:12:07, esprehn wrote:
> > Can you explain this in more detail? I feel like the behaviorAtBoundary
values
> > are not very well understood except for you. :)
> 
> Sure.
> 
> behaviorAtBoundary explains how context.scope works.
> 
> If behaviorAtBoundary is:
> (a) ScopeIsShadowHost, the context.scope works as shadow host. So
context.scope is in shadow trees hosted by the context.scope.
> 
> (b) StayWithinTreescope, SelectorChecker has two scope. One is context.scope
and the other is treescope. context.scope is used for :scope, e.g.
element.querySelector(":host :scope div").
> 
> (c) Otherwise, the context.scope should be a scoping node of a style scoped.
> 
> In (b) and (c) case, context.scope is not a root of shadow trees.
> 
> (a) and (c) is used for styleForElement (ResolvingStyle mode or
CollectingRules mode). (b) is used for querySelector or sharedStyleFinder
(SharingRules or QueryingRules mode).
> 
> So, when sharedStyleFinder wants to check whether some element can reuse an
existing style used by another element or not,
> basically context.scope is not required except :host and :scope.
> 
> :host and :scope depends on where a rule is declared (=context.scope
information).

Awesome, we should get your description of the values added in a comment in the
source too. :)

lgtm

[esprehn, 2014-03-27 13:22:09]

The CQ bit was checked by esprehn@chromium.org

[commit-bot: I haz the power, 2014-03-27 13:22:11]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tasak@google.com/203303002/40001

[commit-bot: I haz the power, 2014-03-27 13:31:35]

Change committed as 170176