Our previously cherry-picked patches are now in 1.3.0. I've (re-)applied
the following patches.

- The old CHROMIUM.diff to remove __DATE__ dependency.

- genmodule was previously patched to add an output argument.
  This was reapplied and then tweaked so the output argument is
  optional, so upstream's build still works. (That simplifies
  the update process in Chromium.)

- genperf prints something to stderr on some non-fatal errors.
  This has been patched out.

- gen_x86_insn.py was previously patched to add an output
  argument. This was discarded because the Chromium build will
  use upstream's pre-generated files, to simplify the build
  and align with upstream.

The patches themselves are in
https://chromium-review.googlesource.com/c/608869 because
README.chromium and the patches are in a different repository.

Bug: 753886
Change-Id: I50c6fa5eebf0e24e4e7ea0ee597a43941b275fec