RenderObject::canHaveChildren()==false prevents shadow renderer creation

[Kent Tamura]

Some renderers return false for canHaveChildren().  So if we try to convert the legacy shadow DOM code to the new API, the shadow nodes won't have their renderers.  See Node::createRendererIfNeeded().

dglazkov said:
> I think it should be a function on an Element which indicates whether its children should be rendered

Source/WebCore/rendering/RenderButton.h:    virtual bool canHaveChildren() const;
Source/WebCore/rendering/RenderDataGrid.h:    virtual bool canHaveChildren() const { return false; }
Source/WebCore/rendering/RenderIndicator.h:    virtual bool canHaveChildren() const { return false; }
Source/WebCore/rendering/RenderListBox.h:    virtual bool canHaveChildren() const { return false; }
Source/WebCore/rendering/RenderMenuList.h:    virtual bool canHaveChildren() const { return false; }
Source/WebCore/rendering/RenderReplaced.h:    virtual bool canHaveChildren() const { return false; }
Source/WebCore/rendering/RenderTableCol.h:    virtual bool canHaveChildren() const;
Source/WebCore/rendering/RenderTextControl.h:    virtual bool canHaveChildren() const { return false; }

[Dimitri Glazkov (Google)]

This is going to be part of <content> element machinery. By default, if the element has shadow DOM subtree, the children aren't rendered, so this decision becomes runtime, not compile-time.

[Dimitri Glazkov (Google)]

(In reply to comment #1)
> This is going to be part of <content> element machinery. By default, if the element has shadow DOM subtree, the children aren't rendered, so this decision becomes runtime, not compile-time.

Turns out that the best solution is just to never render children for Elements that have shadow DOM.

[Hajime Morrita]

Fixed by http://trac.webkit.org/changeset/108758.