[Refactor] Introduce MediaDelegate

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index e97959e8e006721cc4da82e490a3a021dad2393c..936a55071cc2fb286fc14cbafac5176fda240d8c 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -36,6 +36,7 @@
 #include "ash/launcher/launcher_model_util.h"
 #include "ash/magnifier/magnification_controller.h"
 #include "ash/magnifier/partial_magnification_controller.h"
+#include "ash/media_delegate.h"
 #include "ash/new_window_delegate.h"
 #include "ash/root_window_controller.h"
 #include "ash/screen_ash.h"
@@ -665,6 +666,8 @@ Shell::~Shell() {
 
   keyboard_controller_.reset();
   accessibility_delegate_.reset();
+  new_window_delegate_.reset();
+  media_delegate_.reset();
 
 #if defined(OS_CHROMEOS) && defined(USE_X11)
    if (display_change_observer_)
@@ -841,6 +844,7 @@ void Shell::Init() {
   session_state_delegate_.reset(delegate_->CreateSessionStateDelegate());
   accessibility_delegate_.reset(delegate_->CreateAccessibilityDelegate());
   new_window_delegate_.reset(delegate_->CreateNewWindowDelegate());
+  media_delegate_.reset(delegate_->CreateMediaDelegate());
 
   if (!command_line->HasSwitch(views::corewm::switches::kNoDropShadows)) {
     resize_shadow_controller_.reset(new internal::ResizeShadowController());