Add unsafe_layout_node(), unsafe_paintable(), and unsafe_paintable_box()
accessors that skip layout-staleness verification. These are for use in
contexts where accessing layout/paintable data is legitimate despite
layout not being up to date: tree construction, style recalculation,
painting, animation interpolation, DOM mutation, and invalidation
propagation.
Also add wrapper APIs on Node to centralize common patterns:
- set_needs_display() wraps if (unsafe_paintable()) ...set_needs_display
- set_needs_paint_only_properties_update() wraps similar
- set_needs_layout_update() wraps if (unsafe_layout_node()) ...
And add Document::layout_is_up_to_date() which checks whether layout
tree update flags are all clear.
These attributes are consumed during layout in SVGFormattingContext to
compute the viewbox transform. They don't affect the layout tree
structure, so a layout-only invalidation is sufficient instead of a
full layout tree rebuild.
From the SVG spec
The value of the ‘viewBox’ attribute is a list of four numbers <min-x>,
<min-y>, <width> and <height>, separated by whitespace and/or a comma...
Currently try_parse_view_box will fail to parse the attribute if the
values are separated by commas.
This change replaces try_parse_view_box with a more correct
implementation. It will reside in the AttributeParser.cpp. This new
implementation correctly handles comma-separated viewBox values, and is
also more robust against invalid inputs.
Additionally, it adds a new test case to ensure viewBox values with
various syntax are parsed correctly and invalid values are rejected.
Special handling for SVGClipPathElement and SVGMaskElement, which use a
a ViewBox and PreserveAspectRatio value internally, has been moved to
`SVGFormattingContext`.
