@chryw great work I merged it in. I now see the following issues:

• Drag area is misaligned
  

• Arrow missing for top stack frame (yellow) and selected stack frame (green)

• Breakpoint hint decoration takes priority over regular breakpoint decoration. If a user hover over breakpoint it should show that decoration, not the transaparent one

• Start icon in select box looks too big - compare it to debug toolbar
  

• Since you decided to remove the dark theme icons which makes perfect sense I think we can simply remove a lot of css rules. Which you changed to point to the light theme .svg, but instead we can just remove all those rules imho

Let me know if you have time to tackle these issues, if not I can look into fixing some of them. Thanks a lot again!

@chryw so we do not rush with the fixes I have decided to revert the PR temporarily again. Sorry about that, it is my mistake, I should have first tried it out before merging.

Also on top of the issues above, here are two more we get at build time:

CSS INLINING IMAGE AT out-build/vs/workbench/parts/debug/browser/media/continue.svg MORE THAN ONCE. CONSIDER CONSOLIDATING CSS RULES
CSS INLINING IMAGE AT out-build/vs/workbench/parts/debug/browser/media/continue-inverse.svg MORE THAN ONCE. CONSIDER CONSOLIDATING CSS RULES
fs.js:646
  return binding.open(pathModule._makeLong(path), stringToFlags(flags), mode);
                 ^

Error: ENOENT: no such file or directory, open 'out-build/vs/workbench/parts/debug/browser/media/breakpoints-activate-inverse.svg'
    at Object.fs.openSync (fs.js:646:18)
    at Object.fs.readFileSync (fs.js:551:33)
    at out-build/vs/css.build.js:317:28
    at out-build/vs/css.build.js:300:12

Let me know if you need help with any of those and I will be happy to.

@chryw the missing arrow were my fault and I have mixed this on master.
Now I will merge in your PR and do some polish on top of it so it is in a decent state.
Then I will write here what else is missing :)

@chryw merged in your great work. Created this issue #45406 so we can track what else needs to be done. Thanks a lot for your effort