Trying to change the toolset used to build Chromium on Windows is a huge undertaking and will ultimately fail because the Chromium team is moving in another direction (towards VS 2015). And, the toolset may be the wrong thing to change anyway.
Until recently Chromium was designed to run on XP. I'm not sure whether any XP incompatible changes have been committed yet, but I wouldn't be surprised. The safest thing would be to sync to a point about six weeks ago when XP was still supported.
But, that is for the question of targeting XP. If you are trying to build on XP then you may hit other issues. For instance, most XP installs are 32-bit, and Chromium cannot build on a 32-bit OS.
These concerns:
are also not related to building or running Chromium on XP. Debugging and profiling are only necessary after you have successfully created a built that will run.
Once Chromium changes the default toolset to VS 2015 then building on XP will not be possible. VS 2015 requires Windows 7 or higher in order to compile code.
So... if you want to build on XP then make sure you have 64-bit XP, and understand that you will not be able to keep syncing because VS 2015 will soon be required.
If you want to run on XP then make sure you sync to a point prior to when the first XP-incompatible change got committed, which is probably sometime in the last six weeks.