Good news from the official Google AdWords Google+ account (sigh):
In June, we announced (https://goo.gl/TF7dmD) that Chrome will begin pausing many Flash ads by default to improve performance for users. This change is scheduled to start rolling out on September 1, 2015.
Most Flash ads uploaded to AdWords are automatically converted to HTML5.
They also offer a converter for those ads that can’t be automatically rendered in HTML5. This should nicely improve loading performance for many big sites.