linux: Remove all the X and GTK+ related implementations.

Now we only uses GTK+ for app indicator and status icon, also notice the
in Chrome35 the Gtk2StatusIcon class doesn't exist yet so we shipp
related files under chromium_src, remember to delete them after upgraded
to Chrome36.

atom/browser/ui/accelerator_util_views.cc

@@ -0,0 +1,14 @@
+// Copyright (c) 2013 GitHub, Inc. All rights reserved.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#include "atom/browser/ui/accelerator_util.h"
+
+#include "ui/base/accelerators/accelerator.h"
+
+namespace accelerator_util {
+
+void SetPlatformAccelerator(ui::Accelerator* accelerator) {
+}
+
+}  // namespace accelerator_util