Remove SVGDocumentExtensions::IsSVGRootWithRelativeLengthDescendents

It's not used.

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: If6630b2e404108044833ea5512151facdfe7e59d
Reviewed-on: https://chromium-review.googlesource.com/1179760Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#584061}

third_party/blink/renderer/core/svg/svg_document_extensions.cc

@@ -127,11 +127,6 @@ void SVGDocumentExtensions::RemoveSVGRootWithRelativeLengthDescendents(
   relative_length_svg_roots_.erase(svg_root);
 }
 
-bool SVGDocumentExtensions::IsSVGRootWithRelativeLengthDescendents(
-    SVGSVGElement* svg_root) const {
-  return relative_length_svg_roots_.Contains(svg_root);
-}
-
 void SVGDocumentExtensions::InvalidateSVGRootsWithRelativeLengthDescendents(
     SubtreeLayoutScope* scope) {
 #if DCHECK_IS_ON()

third_party/blink/renderer/core/svg/svg_document_extensions.h

@@ -60,7 +60,6 @@ class SVGDocumentExtensions
 
   void AddSVGRootWithRelativeLengthDescendents(SVGSVGElement*);
   void RemoveSVGRootWithRelativeLengthDescendents(SVGSVGElement*);
-  bool IsSVGRootWithRelativeLengthDescendents(SVGSVGElement*) const;
   void InvalidateSVGRootsWithRelativeLengthDescendents(SubtreeLayoutScope*);
 
   bool ZoomAndPanEnabled() const;