New ad ui and click behavior for ima html5 sdk

Starting this week, we're going to incrementally roll out a change in the way the IMA HTML5 SDK handles an ad's UI. We will be adding a Learn More button to Ad Exchange and AdSense ads on both desktop and mobile. Clicking on the button will take the user to the advertiser's site, while clicking elsewhere on the ad will pause or resume it. This is a change from the existing behavior, where clicking anywhere on the ad opens the advertiser's site. The new ad UI....