I faced the same problem. And I tried #4 script.
Then the window also crashed and returned below.
1st time
$ python webkit-bug.py
python: malloc.c:3074: sYSMALLOc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >= (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long)old_end & pagemask) == 0)' failed. Aborted (core dumped)
2nd time
$ python webkit-bug.py python: malloc.c:4591: _int_malloc: Assertion `(unsigned long)(size) >= (unsigned long)(nb)' failed. Aborted (core dumped)
I faced the same problem.
And I tried #4 script.
Then the window also crashed and returned below.
1st time
$ python webkit-bug.py
python: malloc.c:3074: sYSMALLOc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >= (unsigned long)(( ((__builtin_ offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long)old_end & pagemask) == 0)' failed.
Aborted (core dumped)
2nd time
$ python webkit-bug.py
python: malloc.c:4591: _int_malloc: Assertion `(unsigned long)(size) >= (unsigned long)(nb)' failed.
Aborted (core dumped)