For those who doesn't know what WebGL is:
WebGL (Web-based Graphics Library) is a software library that extends the capability of the JavaScript programming language to allow it to generate interactive 3D graphics within any compatible web browser. WebGL code executes on a computer display card's Graphics Processing Unit (GPU), which must support shader rendering.
WebGL is a context of the canvas HTML element that provides a 3D computer graphics API without the use of plug-ins.[2] The specification was released as version 1.0 on March 3, 2011.[1] WebGL is managed by the non-profit Khronos Group.

WebGL is required to play some games or run some applications on Google Chrome e.g. SKID Racer game on Chrome Web Store. WebGL should be activated by default in Google Chrome, if you are unsure about it, please check the WebGL capability by visiting this site and choose whatever test you want. If your Google Chrome supports WebGL, the above picture should appear on your browser.

In case, Google Chrome doesn't activate WebGL capability because unsupported graphics card (such as Intel GMA), you can force it to enable WebGL by executing Google Chrome with "--ignore-gpu-blacklist" argument. Here's is the example:
  • google-chrome --ignore-gpu-blacklist
If you want to add the "--ignore-gpu-blacklist" argument to Google Chrome shortcut on menu or launcher, please open file "/usr/share/applications/google-chrome.desktop" with your favorite text editor (root privileges needed) and change the "Exec" value with the following:
  • /opt/google/chrome/google-chrome --ignore-gpu-blacklist %U
Please see the figure below for more details:

Once edited, save the changes and do a WebGL test.

Regards :)