Will my Mac Pro be able to run WebGL applications?
Here is the answer from Chrome help article: 

You'll need Mac OS 10.5 and Mac OS 10.6 (recommended).
10.7 I believe is also supported.

If you have the following graphics cards, WebGL is unsupported and is disabled by default:


NVIDIA GeForce FX Go5200
ATI Radeon HD2400
ATI Radeon 2600 series
ATI Radeon X1900
GeForce 7300 GT


So, yes, upgrade videocard for WebGL to work.