Revert of Use a stub implementation of GlobalShortcutListener for Athena

Revert of Use a stub implementation of GlobalShortcutListener for Athena (patchset #3 id:100001 of https://codereview.chromium.org/697803002/)

Reason for revert:
This CL breaks GN build on ChromeOS:
http://build.chromium.org/p/chromium.chromiumos/buildstatus?builder=Linux%20ChromiumOS%20GN&number=187

The error message was:
ERROR at //chrome/browser/extensions/BUILD.gn:189:7: Item not found
      "global_shortcut_listener_x11.cc",
      ^--------------------------------
You were trying to remove "global_shortcut_listener_x11.cc"
from the list but it wasn't there.

Original issue's description:
> Use a stub implementation of GlobalShortcutListener for Athena
>
> BUG=426561
> TEST=None
>
> Committed: https://crrev.com/3064611cafd0464e4899dfdf7f485efe71f3ef57
> Cr-Commit-Position: refs/heads/master@{#302578}

TBR=oshima@chromium.org,asargent@chromium.org,pkotwicz@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=426561
Committed: https://crrev.com/0b7420d17a9fa360484ad1dc7fefe15e45f64edb
Cr-Commit-Position: refs/heads/master@{#302580}

[tzik, 2014-11-04 06:20:36]

Created Revert of Use a stub implementation of GlobalShortcutListener for Athena

[commit-bot: I haz the power, 2014-11-04 06:21:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/697343002/1

[commit-bot: I haz the power, 2014-11-04 06:22:13]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-04 06:22:42]

Patchset 1 (id:??) landed as
https://crrev.com/0b7420d17a9fa360484ad1dc7fefe15e45f64edb
Cr-Commit-Position: refs/heads/master@{#302580}