mash: Migrate ShellDelegate ownership and access to WmShell.

ash/accelerators/exit_warning_handler.cc

Index: ash/accelerators/exit_warning_handler.cc
diff --git a/ash/accelerators/exit_warning_handler.cc b/ash/accelerators/exit_warning_handler.cc
index 82e6d0cbacaac189f57d4232b249caaa54aa1670..2b08f2025d0b0a9129c415c56201e80ffa0a9c31 100644
--- a/ash/accelerators/exit_warning_handler.cc
+++ b/ash/accelerators/exit_warning_handler.cc
@@ -4,10 +4,10 @@
 
 #include "ash/accelerators/exit_warning_handler.h"
 
+#include "ash/common/shell_delegate.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/wm_shell.h"
 #include "ash/shell.h"
-#include "ash/shell_delegate.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
@@ -106,7 +106,6 @@ ExitWarningHandler::~ExitWarningHandler() {
 }
 
 void ExitWarningHandler::HandleAccelerator() {
-  ShellDelegate* shell_delegate = Shell::GetInstance()->delegate();
   switch (state_) {
     case IDLE:
       state_ = WAIT_FOR_DOUBLE_PRESS;
@@ -119,7 +118,7 @@ void ExitWarningHandler::HandleAccelerator() {
       CancelTimer();
       Hide();
       WmShell::Get()->RecordUserMetricsAction(UMA_ACCEL_EXIT_SECOND_Q);
-      shell_delegate->Exit();
+      WmShell::Get()->delegate()->Exit();
       break;
     case EXITING:
       break;