Comment 9 for bug 1401488

The first, and probably the primary, error is this:

==18516== Invalid read of size 4
==18516== at 0x71F518A: g_source_iter_next (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4302.0)
==18516== by 0x71F7A7E: g_main_context_check (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4302.0)
==18516== by 0x71F80EF: g_main_context_iterate.isra.29 (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4302.0)
==18516== by 0x71F825B: g_main_context_iteration (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4302.0)
==18516== by 0x4EC337C: mir::GLibMainLoop::run() (glib_main_loop.cpp:126)
==18516== by 0x4E89EA0: mir::DisplayServer::run() (display_server.cpp:223)
==18516== by 0x4E850E2: mir::run_mir(mir::ServerConfiguration&, std::function<void (mir::DisplayServer&)>, std::function<void (int)> const&) (run_mir.cpp:113)
==18516== by 0x4E84CB7: mir::run_mir(mir::ServerConfiguration&, std::function<void (mir::DisplayServer&)>) (run_mir.cpp:68)
==18516== by 0x4702A0: main (demo_shell.cpp:158)
==18516== Address 0xa857918 is 24 bytes inside a block of size 296 free'd
==18516== at 0x4C2BE10: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==18516== by 0x71F5011: g_source_unref_internal (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4302.0)
==18516== by 0x4EC9FCD: mir::detail::GSourceHandle::~GSourceHandle() (glib_main_loop_sources.cpp:94)
==18516== by 0x4EC2D3D: (anonymous namespace)::AlarmImpl::cancel() (glib_main_loop.cpp:48)
==18516== by 0x4FBD3A4: (anonymous namespace)::TimeoutFrameDroppingPolicy::swap_unblocked() (timeout_frame_dropping_policy_factory.cpp:74)