chromeos: Migrate SignOut and RequestRestartForUpdate to mojo interface

ash/common/wm_shell.cc

Index: ash/common/wm_shell.cc
diff --git a/ash/common/wm_shell.cc b/ash/common/wm_shell.cc
index 98cd1ce22545b277ab2d90a4e63d492738722820..c0c4268ad0642918b70a373fb64beaacaeacbfb4 100644
--- a/ash/common/wm_shell.cc
+++ b/ash/common/wm_shell.cc
@@ -355,15 +355,17 @@ void WmShell::SetSystemTrayDelegate(
   system_tray_delegate_ = std::move(delegate);
   system_tray_delegate_->Initialize();
 #if defined(OS_CHROMEOS)
+  // Accesses WmShell in its constructor.

[James Cook, 2016/11/15 22:43:18]

I left this where it is because WmShell is probably going to go away, or be
folded into ash::Shell, in the next couple months. Initialization of the
LogoutConfirmationController could probably move into WmShell::Initialize() but
destruction looks like it needs to happen before all windows are closed, so I
would have to introduce a DeleteLogoutConfirmationController method.

   logout_confirmation_controller_.reset(new LogoutConfirmationController(
-      base::Bind(&SystemTrayDelegate::SignOut,
-                 base::Unretained(system_tray_delegate_.get()))));
+      base::Bind(&SystemTrayController::SignOut,
+                 base::Unretained(system_tray_controller_.get()))));
 #endif
 }
 
 void WmShell::DeleteSystemTrayDelegate() {
   DCHECK(system_tray_delegate_);
 #if defined(OS_CHROMEOS)
+  // Accesses WmShell in its destructor.
   logout_confirmation_controller_.reset();
 #endif
   system_tray_delegate_.reset();