Move more from WmShell to Shell

ash/common/system/chromeos/brightness/tray_brightness.cc

Index: ash/common/system/chromeos/brightness/tray_brightness.cc
diff --git a/ash/common/system/chromeos/brightness/tray_brightness.cc b/ash/common/system/chromeos/brightness/tray_brightness.cc
index c67af999c5cc3670f64d8ebfaed1ab7a0ab5a9af..4a6cbdbc82f0cb2ee0800b4fb8a1c369441e3d80 100644
--- a/ash/common/system/chromeos/brightness/tray_brightness.cc
+++ b/ash/common/system/chromeos/brightness/tray_brightness.cc
@@ -160,7 +160,7 @@ void BrightnessView::SliderValueChanged(views::Slider* sender,
   if (reason != views::VALUE_CHANGED_BY_USER)
     return;
   BrightnessControlDelegate* brightness_control_delegate =
-      WmShell::Get()->brightness_control_delegate();
+      Shell::Get()->brightness_control_delegate();
   if (brightness_control_delegate) {
     double percent = std::max(value * 100.0, kMinBrightnessPercent);
     brightness_control_delegate->SetBrightnessPercent(percent, true);
@@ -202,7 +202,7 @@ TrayBrightness::~TrayBrightness() {
 
 void TrayBrightness::GetInitialBrightness() {
   BrightnessControlDelegate* brightness_control_delegate =
-      WmShell::Get()->brightness_control_delegate();
+      Shell::Get()->brightness_control_delegate();
   // Worrisome, but happens in unit tests, so don't log anything.
   if (!brightness_control_delegate)
     return;