IsShadowRootFlag should not depend on whether the ShadowRoot is attached to a host

• Component: DOM
• Status: RESOLVED FIXED

[Dominic Cooney]

To improve performance I am proposing we use IsShadowRootFlag and isSVGShadowRoot virtual slightly differently:

getFlag(IsShadowRootFlag) => ShadowRoot or SVGShadowRoot
getFlag(IsShadowRootFlag) && !getFlag(IsSVGElementFlag) => ShadowRoot (ie new style)
getFlag(IsShadowRootFlag) && getFlag(IsSVGElementFlag) => SVGShadowRoot

This will fix a performance regression in parentNode (see bug 69266) and remove a virtual from Node (isSVGShadowRoot can just consult flags.)

One way isSVGShadowRoot and getFlag(IsShadowRootFlag) vary today is that isSVGShadowRoot is associated with the SVGShadowRoot type the vtable; it never changes for a given instance. But ShadowRoot sets and clears getFlag(IsShadowRootFlag) when a ShadowRoot is attached/detached to a host. I think this is needless variation. I think we should always set IsShadowRootFlag for ShadowRoot instances. If the caller wants to find out whether it is associated with a host, it can test null-ness of shadowHost().

[Dominic Cooney]

Created attachment 109757 [details]
Patch

[Hajime Morrita]

Comment on attachment 109757 [details]
Patch

Looks sane.

[WebKit Review Bot]

Comment on attachment 109757 [details]
Patch

Clearing flags on attachment: 109757

Committed r96782: <http://trac.webkit.org/changeset/96782>

[WebKit Review Bot]

All reviewed patches have been landed.  Closing bug.