Refactors keyboard related code so mash can use a keyboard

ash/mus/mojo_shell.h

Index: ash/mus/mojo_shell.h
diff --git a/ash/mus/mojo_shell.h b/ash/mus/mojo_shell.h
new file mode 100644
index 0000000000000000000000000000000000000000..a38713b4e7d4b5b73b8b8bf115adbac216dcb869
--- /dev/null
+++ b/ash/mus/mojo_shell.h
@@ -0,0 +1,18 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_MUS_MOJO_SHELL_H_
+#define ASH_MUS_MOJO_SHELL_H_
+
+namespace mojo {
+class Shell;
+}
+
+namespace ash {
+
+mojo::Shell* GetMojoShell();
+
+}  // namespace ash
+
+#endif  // ASH_MUS_MOJO_SHELL_H_