I just sent a proposal to the WICG for an asynchronous Clipboard API: https://discourse.wicg.io/t/proposal-modern-asynchronous-clipboard-api/1513
(yes, I know. Not the first time something like this has been proposed <https://lists.w3.org/Archives/Public/public-webapps/2015JulSep/0235.html>) This is a follow-up to an earlier thread Clipboard API: remove dangerous formats from mandatory data types <https://lists.w3.org/Archives/Public/public-webapps/2015AprJun/0819.html> where Chrome is unable to safely add clipboard support for a number of image formats. An async API would allow these image formats to be supported (because the sanitization could happen without blocking the main thread).
