Revert of Linux Aura accessibility is enabled only on GNOME desktops (patchset #15...

Revert of Linux Aura accessibility is enabled only on GNOME desktops (patchset #15 id:280001 of https://codereview.chromium.org/1028553003/)

Reason for revert:
All linux perf bots red, failing on various blink_perf tests. Speculatively reverting this CL since several bisects pointed to it.

BUG=485590

Original issue's description:
> Linux Aura accessibility is enabled only on GNOME desktops
>
> Linux Aura accessibility is not enabled on desktops different than GNOME2.
> GNOME3 has deprecated gconf in favor of gsettings and dconf.
> AT-SPI (cross-platform framework that provides communication between AT
> and application) bus launcher has a property called org.a11y.Bus.IsEnabled
> that could be easily read by dbus call.
>
> In generall this patch adds an additional check to enable accessibility.
> When gconf is available use gnome's accessibility key otherwise
> org.a11y.Bus.IsEnabled property.
>
> BUG=472183,468989,468112
> TBR=stevenjb@chromium.org,jochen@chromium.org
>
> Committed: https://crrev.com/16e2d5a386e3ddd5be818a0d27610b1e9ee9c08e
> Cr-Commit-Position: refs/heads/master@{#328651}

TBR=dmazzoni@chromium.org,plundblad@chromium.org,l.gombos@samsung.com,jochen@chromium.org,stevenjb@chromium.org,dpranke@chromium.org,k.czech@samsung.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=472183,468989,468112

Review URL: https://codereview.chromium.org/1124173005

Cr-Commit-Position: refs/heads/master@{#329404}