Today, more than 90% of Flash on the web loads behind the scenes to support things like page analytics. This kind of Flash slows you down, and starting this September, Chrome 53 will begin to block it. HTML5 is much lighter and faster, and publishers are switching over to speed up page loading and save you more battery life. You’ll see an improvement in responsiveness and efficiency for many sites.
Google plans to take this one step further in December with Chrome 55 which will make HTML5 the default experience, except for sites which only support Flash. When visiting those sites, you'll be prompted to enable Flash at your first visit.
More details at the link below...