Bug 249141 – [LBSE] Do not relayout on dynamic transform changes, if not necessary

• Status: RESOLVED
• Resolution: FIXED
• Component: SVG

[Nikolas Zimmermann]

The legacy SVG engine always had to perform relayouts when the transform
of an element changed (up to the containing block, stopping at RenderSVGRoot
boundary in case of mixed SVG/HTML documents). Container position and sizes
were affected by the transformations of the descendants. That's no longer the 
case in LBSE, which follows CSS/HTML style of making transformations a paint
effect, not inducing costly relayouts.
    
However this only works if SVG <text> elements are not involved: SVG text
always needs a relayout, as the "screen font size scaling factor" depends on
the CTM of the transformed element (all transformations from target element
up to RenderSVGRoot enter the calculation).

The patch will present a solution for that, giving us transform updates
without relayouts for everything except text, which is a good start.

[Nikolas Zimmermann]

Pull request: https://github.com/WebKit/WebKit/pull/7482

[Radar WebKit Bug Importer]

<rdar://problem/103512891>

[EWS]

Committed 259158@main (b348ce7635b6): <https://commits.webkit.org/259158@main>

Reviewed commits have been landed. Closing PR #7482 and removing active labels.