[Refactor] Introduce MediaDelegate

ash/shell/shell_delegate_impl.cc

Index: ash/shell/shell_delegate_impl.cc
diff --git a/ash/shell/shell_delegate_impl.cc b/ash/shell/shell_delegate_impl.cc
index 717d07d42ad265cc452335eaf646591e7968b137..218216d914e0ce0db2e4e7496c737800d23473e6 100644
--- a/ash/shell/shell_delegate_impl.cc
+++ b/ash/shell/shell_delegate_impl.cc
@@ -10,6 +10,7 @@
 #include "ash/default_user_wallpaper_delegate.h"
 #include "ash/host/root_window_host_factory.h"
 #include "ash/keyboard_controller_proxy_stub.h"
+#include "ash/media_delegate.h"
 #include "ash/new_window_delegate.h"
 #include "ash/session_state_delegate.h"
 #include "ash/session_state_delegate_stub.h"
@@ -51,6 +52,19 @@ class NewWindowDelegateImpl : public NewWindowDelegate {
   DISALLOW_COPY_AND_ASSIGN(NewWindowDelegateImpl);
 };
 
+class MediaDelegateImpl : public MediaDelegate {
+ public:
+  MediaDelegateImpl() {}
+  virtual ~MediaDelegateImpl() {}
+
+  virtual void HandleMediaNextTrack() OVERRIDE {}
+  virtual void HandleMediaPlayPause() OVERRIDE {}
+  virtual void HandleMediaPrevTrack() OVERRIDE {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MediaDelegateImpl);
+};
+
 }  // namespace
 
 ShellDelegateImpl::ShellDelegateImpl()
@@ -139,6 +153,10 @@ ash::NewWindowDelegate* ShellDelegateImpl::CreateNewWindowDelegate() {
   return new NewWindowDelegateImpl;
 }
 
+ash::MediaDelegate* ShellDelegateImpl::CreateMediaDelegate() {
+  return new MediaDelegateImpl;
+}
+
 aura::client::UserActionClient* ShellDelegateImpl::CreateUserActionClient() {
   return NULL;
 }
@@ -146,15 +164,6 @@ aura::client::UserActionClient* ShellDelegateImpl::CreateUserActionClient() {
 void ShellDelegateImpl::RecordUserMetricsAction(UserMetricsAction action) {
 }
 
-void ShellDelegateImpl::HandleMediaNextTrack() {
-}
-
-void ShellDelegateImpl::HandleMediaPlayPause() {
-}
-
-void ShellDelegateImpl::HandleMediaPrevTrack() {
-}
-
 ui::MenuModel* ShellDelegateImpl::CreateContextMenu(aura::Window* root) {
   return new ContextMenu(root);
 }