Display dimming entirely when visiting specific web page using Safari (Mid-2015 MBP with Radeon R9 M370X)

Hello

I have a 2 day old 15-inch Mid-2015 Retina Macbook Pro (2.5GHz i7 16GB DDR3 512GB SSD with AMD Radeon R9 M370X) running 10.10.3 with all latest updates applied.

When visiting http://www.google.com/chrome/ using Safari 8.0.6 the display almost always dims entirely and then reappears, all within about 1 second. Refreshing the page usually triggers the dimming issue again.

However this only happens when the 'Automatic graphics switching' preference in Energy Saver is enabled and WebGL is enabled within Safari. It seems perhaps the WebGL element on the web page triggers the switch from the integrated to discrete graphics card. I appreciate this may be typical behaviour but just wondered whether anyone else with the same Macbook Pro can replicate this? I'd like to rule it out as a hardware issue while still in warranty. I've restarted the machine several times, repaired disk permissions and haven't loaded any third party software or drivers yet (other than a few App Store apps).

I visited an Apple Store this evening but unfortunately they didn't have the same model on display.

Any help would be greatly appreciated,

Many thanks!