Works on my setup: chromium 44.0.2403.157, Arc Welder 44.4410.376.15, Pleco version 3.2.15 on Linux 4.1.6-1-ARCH.
Has it ever worked before, and stopped working after an update of either Pleco, chrome or arc welder? Maybe reinstalling (and first removing all configuration files of) chrome and arc welder helps? I remember having had a “similar” problem with a very dated version of arc welder, some months ago.