Change Google Chrome cache size on OS X

You would have to launch it from the command line with the following flag --disk-cache-size=524288000, where 524288000 is the upper limit of what it could be set to.
You could try to make a script that launches it with the augment.

Something like:

#!/bin/sh

/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --disk-cache-size=524288000 &

Then name it with a .sh extension, and chmod u+x /path/to/file.sh and you should be good.