SVGRenderSupport contains the SVGRenderBase class, which was meant to be a base class for all SVG renders until all inherit from RenderSVGModelObject, introduced by Eric a year ago.
RenderSVGModelObject inherits from RenderObject. That means classes like RenderSVGImage, which inherits from RenderImage, can NOT inherit from RenderSVGModelObject, as RenderImage already inherits from RenderObject.
The whole class is uncessary and confusing. I'll rename it to SVGRenderSupport, just like the file name, and make all methods static and make it impossible to construct the class.
This shrinks the size of all SVG renderers.
Created attachment 60019 [details]
Attachment 60019 [details] did not pass style-queue:
Failed to run "['WebKitTools/Scripts/check-webkit-style', '--no-squash']" exit_code: 1
WebCore/rendering/RenderSVGResourcePattern.cpp:28: Alphabetical sorting problem. [build/include_order] 
Total errors found: 1 in 32 files
If any of these errors are false positives, please file a bug against check-webkit-style.
Comment on attachment 60019 [details]
LGTM. Fix the alphabetic order and you can land it. r=me.
Landed in r62117.
Oops, that should be: 62118.