Refactors keyboard related code so mash can use a keyboard

ash/mus/sysui_application.cc

Index: ash/mus/sysui_application.cc
diff --git a/ash/mus/sysui_application.cc b/ash/mus/sysui_application.cc
index 15339110cf731197f368915793d501dcf820dff9..76eff550617a593e27b3ffa65b98e9fdbd0a18cd 100644
--- a/ash/mus/sysui_application.cc
+++ b/ash/mus/sysui_application.cc
@@ -7,6 +7,7 @@
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/host/ash_window_tree_host_init_params.h"
 #include "ash/host/ash_window_tree_host_platform.h"
+#include "ash/mojo_shell.h"
 #include "ash/mus/shell_delegate_mus.h"
 #include "ash/mus/stub_context_factory.h"
 #include "ash/root_window_settings.h"
@@ -129,6 +130,8 @@ class AshInit {
   aura::Window* root() { return ash::Shell::GetPrimaryRootWindow(); }
 
   void Initialize(mojo::Shell* shell) {
+    SetMojoShell(shell);
+
     aura_init_.reset(new views::AuraInit(shell, "views_mus_resources.pak"));
     views::WindowManagerConnection::Create(shell);