Condition the use of ChromeBrowserMainExtraPartsViewsLinux to !use_ozone

In order to bring up a Chrome/Chromium Ozone/Wayland build,
it is needed to opt out the instantiation/inclusion of
chrome_browser_main_extra_parts_views_linux.cc/h in Ozone builds.

It should still possible to opt-in the use of CBMEPVL for Ozone builds
in the future, but it would be safer to condition it to an extra GN variable,
where one could explicitly specify that the Gtk wayland backend is to be used.
E.g.:

  if (!use_ozone || use_gtk_wayland_backend) {
    sources += [
      "views/chrome_browser_main_extra_parts_views_linux.cc",
      "views/chrome_browser_main_extra_parts_views_linux.h"
    ]
  } else # regular ozone case {
    sources += [
      "views/chrome_browser_main_extra_parts_views.cc",
      "views/chrome_browser_main_extra_parts_views.h"
    ]
  }

CL also moves the PreProfileInit override from CBMEPVL to CBMEPV,
if-def'ing it out for CHROMEOS, in order to keep the behavior to
desktop linux builds (x11/ozone).

BUG=295089

Review-Url: https://codereview.chromium.org/2462423002
Cr-Commit-Position: refs/heads/master@{#429391}
6 files changed