After investigation I discovered that the hardware acceleration had been disabled. By adding the following switches to the 'exec' lines in /opt/google/chrome/google-chrome I was able to force all the acceleration options on:
I added these to the file by editing it with root (sudo) options. I suspect the file will be overwritten on update. There seems to be an environment variable for chromium which allows you to set command line options to pass to chromium without editing files, but I can't tell if this works for Chrome yet.