Slow assets download in Chrome browser

Hello, I'm having a huge issue with Chrome browsers: at the start of the game, the unity client has to download Asset Bundles. On several machines, this download is very slow (like 10 to 40 Kb/s). What is very weird is that as soon as I switched tab or a new tab is opened in the browser (even if the tab is the parameters tab), the download highly accelerate to 1 Mb/s or more! If I go back to my game's tab, the download slow down again. I also reported this bug to google.

Precisions on the machines where I managed to reproduce this bug:

• We have the issue on several machines, at work place and at home place.

• Chrome is up to date

• No extension are active

• No malware present on the machines

• We reproduced on Win7 & Win8 machines

• No firewall

• No antivirus

• Bug reproductible only in Chrome browser (and not on all machines)

• We are not using NaCl

Any idea / workaround would be great!