Today, my distro (PCLinuxOS) updated to gcc v9.2 (from gcc v8.3.1) and I could reproduce this issue.
However, I cannot explain it beside a compiler bug: the Dullahan version based on the boost API works just fine, while the one based on the standard C++ API crashes lamentably (the code being otherwise exactly the same in both CEF and the plugin: it's just about using either boost::function and boost::bind, or std::function and std::bind !).
It could be a compiler bug, or a libstdc++ library bug, however I also got the same issue when using clang v8.0.1 (or v8.0.0) as the compiler, including when the C++ standard library was still gcc v8.3.1's one (and gcc v8.3.1 and its library work just fine in this respect)... So, either it's a bug in both gcc v9 and clang v8, or it's something in Dullahan or CEF (but I can't see why the latter two would work just fine with gcc v4.6 to 8.3, VS2013 and VS2017).
In any case, I will change the CEF plugin code to use my good old boost-API Dullahan version when either gcc 9+ or clang are used to compile the viewer.
Note that, for now, I would advise anyone caring about the viewer stability to keep compiling it with gcc v8 or older:
gcc v9 and clang got known issues with savage eliminations (bogus "optimizations") of NULL pointer checks and, in gcc v9 case, even with the -fno-delete-null-pointer-checks compiler option in use (an option clang lacks cruelly).