Both blassy and I have seen a bug where the address bar is scrolls off the screen but the page content does not move. In addition switching tabs does not update the visible layer. We have only seen this on Android 4.3.
Video of the behavior http://www.youtube.com/watch?v=v8bLTgg5P0E
I have seen this on the Nexus 10, as one of the manifestations of bug 900020. Based on bug 900020 comment 20 it may very well be not limited to the mali driver and could occur on other devices. So this might be the same bug as that.
STR: * enable don't keep activities * Start fennec * open another app that has URLs * open the link in fennec * rotate fennec while the page is loading
Can you retest on a build with bug 900020 fixed? Turns out that affected all of the Android 4.3 devices because Android 4.3 has OpenGL ES 3.0 and we weren't handling that properly. So it should fix this bug as well.