Polygons filling takes dozens of minutes.

Description

I'm quite sure that it shouldn't be like this. Polygons filling takes far too long time (about 30 minutes for following example)

Steps to reproduce

Open attached file with pcbnew and start polygons refill ("Fill all zones") (B). rex.kicad_pcb

KiCad Version

Application: Pcbnew

Version: (5.99.0-3447-gb3a369bd7), debug build

Libraries:
	wxWidgets 3.0.5
	libcurl/7.72.0 OpenSSL/1.1.1g zlib/1.2.11 zstd/1.4.5 libidn2/2.3.0 libpsl/0.21.0 (+libidn2/2.2.0) libssh2/1.9.0 nghttp2/1.41.0

Platform: Linux 5.8.2-arch1-1 x86_64, 64 bit, Little endian, wxGTK

Build Info:
	Date: Sep 20 2020 23:06:46
	wxWidgets: 3.0.5 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.72.0
	OCC: 7.4.0
	Curl: 7.72.0
	ngspice: 32
	Compiler: GCC 10.2.0 with C++ ABI 1014

Build settings:
	KICAD_SCRIPTING=ON
	KICAD_SCRIPTING_MODULES=ON
	KICAD_SCRIPTING_PYTHON3=ON
	KICAD_SCRIPTING_WXPYTHON=ON
	KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
	KICAD_SCRIPTING_ACTION_MENU=ON
	BUILD_GITHUB_PLUGIN=ON
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON
	KICAD_STDLIB_DEBUG=OFF
	KICAD_STDLIB_LIGHT_DEBUG=OFF
	KICAD_SANITIZE=OFF