TL,DR (Too Long, Didn’t Read)
Chrome has disabled support for NPAPI which Flashplayer used to be built on. Chrome developers created their own Flashplayer that will work without NPAPI so there will be no noticeable difference to the user when viewing ads or running Flash in the Chrome browser.
Putting the Rumors to Rest
There have been some rumors swirling around that with the new Chrome update, The Adobe Flashplayer in the browser will start behaving like Safari where the user will have to explicitly enable a flash animation to play. This will not be the case.
The newly released version of Chrome 42 addresses many issues like ad injectors and crashes but the largest change has been a year coming. Google has disabled NPAPI (Netscape API), essentially turning off plugins such as Java and Silverlight by default.
NPAPI is a 1990’s era technology that extended browsers capabilities including audio and video but it has also been the top culprit in browser crashes and slow-downs, as well as security incidents and increase in code complexity.
The Adobe Flashplayer plugin that banners are run on was originally built using NPAPI and still runs on it in other browsers but Google announced the move from NPAPI a year ago and started building their own version of the Flashplayer which has been integrated into Chrome a year ago.
The main consequence this has for ad serving is that web developers will need to focus on cross browser HTML5 solutions to accomplish what they once did with NPAPI. This will enlarge the HTML5 developer base and require more innovation and standards across browsers.
News with the misleading title:
Chrome Blogs documenting the change all the way back to 2012
Alternatives to NPAPI