Under e10s, calling canvas.drawWindow() with a chrome window will draw the chrome window but draw white/blank for any inner content. e.g. drawWindow() on the browser window will draw the tab UI, etc. but not the current web content. The devtools eyedropper tool relies on this working.

Hmm, this might be interesting to fix. We don't want sync drawWindow calls from the parent. We do have support for remote thumbnailing now through PageThumbs, maybe dev tools can work with that instead?

For the e10s version of the responsive mode , I take a screenshot in the content process and send it back to the main process. See bug 1067145.

I went the route in comment 2. Seems like it would be hard or bad to implement synchronously, so I'm wontfixing.