Webkit crash in Epiphany and others when closing tab

System: A freshly installed Ubuntu 13.04 on i386.

I first discovered this bug in Liferea, the feed reader, but discovered that it appears in the same way in Epiphany and thus conclude that the problem is in libwebkitgtk. The program crashes when closing tabs of certain pages.

Steps to reproduce in Epiphany:
1. Open Epiphany
2. Open a new tab with the page http://haggstrom.blogspot.se/ (a quite ordinary Blogspot blog that for some reason triggers this bug)
3. Close the tab
4. Epiphany crashes (if it doesn't, try repeating steps 2 and 3)

Epiphany then gives the following output:

(epiphany-browser:16336): Gdk-ERROR **: The program 'epiphany-browser' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadDrawable (invalid Pixmap or Window parameter)'.
  (Details: serial 9498 error_code 9 request_code 62 minor_code 0)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the GDK_SYNCHRONIZE environment
   variable to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)
Trace/breakpoint trap (core dumped)

I've installed debug packages for x11-6, libwebkitgtk-3.0.0, libglib2.0.0, libgtk3-0 and libcairo-2 and then issued:

GDK_SYNCHRONIZE=yes gdb epiphany-browser

A backtrace from this gdb is attached.

I also submitted this bug through apport, but I don't know how to find this bug in the issue tracker so I can link or add to it. I could attach the /var/crash file if that helps.