Add ShellDelegate, MediaDelegate and KeyboardUI stubs to mus ash

ash/mus/bridge/wm_shell_mus.cc

Index: ash/mus/bridge/wm_shell_mus.cc
diff --git a/ash/mus/bridge/wm_shell_mus.cc b/ash/mus/bridge/wm_shell_mus.cc
index b9626529759b2ad657d98e7bc909056ddf7d29fb..159124b285d49d258398ab9b49f67360d5400f54 100644
--- a/ash/mus/bridge/wm_shell_mus.cc
+++ b/ash/mus/bridge/wm_shell_mus.cc
@@ -4,9 +4,13 @@
 
 #include "ash/mus/bridge/wm_shell_mus.h"
 
+#include <utility>
+
 #include "ash/common/default_accessibility_delegate.h"
 #include "ash/common/display/display_info.h"
+#include "ash/common/keyboard/keyboard_ui.h"
 #include "ash/common/session/session_state_delegate.h"
+#include "ash/common/shell_delegate.h"
 #include "ash/common/shell_observer.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/system/tray/default_system_tray_delegate.h"
@@ -119,10 +123,10 @@ class AccessibilityDelegateMus : public DefaultAccessibilityDelegate {
 
 }  // namespace
 
-WmShellMus::WmShellMus(ShellDelegate* delegate,
+WmShellMus::WmShellMus(std::unique_ptr<ShellDelegate> shell_delegate,
                        ::ui::WindowTreeClient* client,
                        shell::Connector* connector)
-    : WmShell(delegate),
+    : WmShell(std::move(shell_delegate)),
       client_(client),
       connector_(connector),
       session_state_delegate_(new SessionStateDelegateStub) {
@@ -134,7 +138,11 @@ WmShellMus::WmShellMus(ShellDelegate* delegate,
   CreateMruWindowTracker();
 
   accessibility_delegate_.reset(new AccessibilityDelegateMus(connector_));
+  SetMediaDelegate(base::WrapUnique(delegate()->CreateMediaDelegate()));

[msw, 2016/07/14 19:50:05]

q: Would it make sense to move the corresponding ash::Shell init to WmShellAura?
(and similar for accessibility, etc? it'd be nice to reduce ash::Shell's duties)

[James Cook, 2016/07/14 20:54:44]

I think the right thing to do here is to have the WmShell constructor call
delegate->CreateMediaDelegate() and eliminate the SetMediaDelegate() method. I
didn't do that here because it substantially changes the ordering of
initialization of some media code in Chrome.  I'll give it a try in a follow-on
CL so it'll be easily blame-able if I break something.

[msw, 2016/07/14 20:58:04]

Acknowledged.

   SetSystemTrayDelegate(base::WrapUnique(new DefaultSystemTrayDelegate));
+
+  // TODO(jamescook): Port ash::sysui::KeyboardUIMus and use it here.
+  SetKeyboardUI(KeyboardUI::Create());
 }
 
 WmShellMus::~WmShellMus() {