Moves maintaining ShellObservers back to Shell

ash/display/screen_orientation_controller_chromeos.cc

Index: ash/display/screen_orientation_controller_chromeos.cc
diff --git a/ash/display/screen_orientation_controller_chromeos.cc b/ash/display/screen_orientation_controller_chromeos.cc
index 90742cfbcf5c77cbbebd73ba2331f497ece1cb75..1d21455d03144547cd197229bb60447f3be8b06d 100644
--- a/ash/display/screen_orientation_controller_chromeos.cc
+++ b/ash/display/screen_orientation_controller_chromeos.cc
@@ -68,11 +68,11 @@ ScreenOrientationController::ScreenOrientationController()
       rotation_locked_orientation_(blink::WebScreenOrientationLockAny),
       user_rotation_(display::Display::ROTATE_0),
       current_rotation_(display::Display::ROTATE_0) {
-  WmShell::Get()->AddShellObserver(this);
+  Shell::GetInstance()->AddShellObserver(this);
 }
 
 ScreenOrientationController::~ScreenOrientationController() {
-  WmShell::Get()->RemoveShellObserver(this);
+  Shell::GetInstance()->RemoveShellObserver(this);
   chromeos::AccelerometerReader::GetInstance()->RemoveObserver(this);
   WmShell::Get()->RemoveDisplayObserver(this);
   Shell::GetInstance()->activation_client()->RemoveObserver(this);