I've been seeing this bug most recently in Yosemite 10.10.4 (14E46). It was in prior versions but I wasn't keeping track.
When I resume from sleep my browser windows are cropped in both Firefox and Chrome. Pretty much only the top left corner of the browser window is the view. I can resize the window but the scrollbars remain on this little ~640x480ish view.
The attached screenshot illustrates the issue. If I refresh the window the page resumes and consumes the full window size.
One way to get the window back to normal is to refresh, but I have to do that for every tab that is cropped (and not all windows/tabs are cropped). If I show and hide the bookmarks toolbar in Firefox all windows are fixed.
Any ideas? I can't find any other reports of this bug, but it's happened on two different MacBook Pros of mine. The most recent is: (Retina, 15-inch, Mid 2014, NVIDIA GeForce GT 750M)