This change updates how brave/chromium_src overrides can reference original files: it adds ability to use #include <...> along with #include "src/...". This is enabled by replacing -I../../brave/chromium_src with -iquote../../brave_chromium_src, which adds an include search path only for #include "..." directives.
With this approach, other files in the build tree can reference brave/chromium_src overrides using #include "...", while the overrides themselves can reference original Chromium files using #include <...>. Since Chromium uses #include "..." for all in-tree files, we can leverage this convention and configure our overrides so that we can drop support for #include "src/" later by removing -I../../.. and making rbe_exec_root modification obsolete (the main goal).
Aleksei Khoroshilov