"I ended up with AdobeAAMDetect, Shockwave Flash and Unity Player disabled with Silverlight and OpenH264 Video Codec plugins enabled."
Those three (well, 2, i don;t recognise the AdobeAMM thing) are KNOWN for memory leaks. Unity-in-browser beign the worst offender.
Flash sometimes runs rampant and hogs resources - and it's a little worrying when there's no flash being used!
Update - the AMM thing is related to Adobe cloud useage. The standalone AMM is the lic manager, the browser plugin can be disabled if you don't faff with cloud.