pkg/51350: www/firefox from pkgsrc 2016Q2 fails to build on NetBSD/i386 6.1.5

[ball%cyberspace.org@localhost]

>Number:         51350
>Category:       pkg
>Synopsis:       www/firefox from pkgsrc 2016Q2 fails to build on NetBSD/i386 6.1.5
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jul 20 21:40:00 +0000 2016
>Originator:     Andrew Ball
>Release:        NetBSD/i386 6.1.5 and pkgsrc 2016Q2
>Organization:
>Environment:
NetBSD mwo-c9kdw31 6.1.5 NetBSD 6.1.5 (GENERIC) i386
>Description:
When I attempt to build www/firefox on NetBSD/i386 6.1.5 from pkgsrc 2016Q2, the build fails with...

/usr/pkgsrc/www/firefox/work/firefox-47.0/gfx/skia/skia/src/core/SkScaleToSides.h:52:61:
error: 'nexttowardf' was not declared in this scope
newMaxRadius = nexttowardf(newMaxRadius, 0.0);

A full transcript of the build attempt may be found at http://grex.org/~ball/firefox.log and I am happy to help with further testing.
>How-To-Repeat:
cd /usr/pkgsrc/www/firefox
make fetch-list|sh
make

>Fix:
Unknown.