I have the same problem. I see flakes all over the video on youtube. I also see flakes when I opt in in the HTML5 trial on Youtube. This is a well known issue and you can see the solution below.https://code.google.com/p/chromium/issu ... &id=124569
I have tried the solution and it works. But I don't want to start enabling and disabling Chrome features without knowing the repercussions. So I did something simpler while waiting for Google to fix it. I disabled Flash 11.6 in Chrome and let Flash plugin 11.2 r202 do the job.
You have to go to Settings-Advanced Settings-Privacy-Content Settings-Plugins-Individual plugins. Find Flash plugin 11.6.602.171 and disable it. I also opted out from the Youtube HTML5 trial so that Flash plugin 11.2 r202 does all the work.
Hopefully Google will fix it soon