mash: Minor ash/common fixes for tray_display.

Just fixes some low hanging fruit here.
(other big deps on DisplayManager; ScreenOrientationController)

BUG=619636
TEST=compiles; unit tests; no behavior changes.
R=jamescook@chromium.org

Review-Url: https://codereview.chromium.org/2131823003
Cr-Commit-Position: refs/heads/master@{#404516}

ash/system/chromeos/tray_display.cc

@@ -18,7 +18,6 @@
 #include "ash/common/wm_shell.h"
 #include "ash/display/display_manager.h"
 #include "ash/display/screen_orientation_controller_chromeos.h"
-#include "ash/display/window_tree_host_manager.h"
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray.h"
 #include "base/bind.h"
@@ -299,12 +298,12 @@ class DisplayView : public ActionableView {
 
 TrayDisplay::TrayDisplay(SystemTray* system_tray)
     : SystemTrayItem(system_tray), default_(NULL) {
-  Shell::GetInstance()->window_tree_host_manager()->AddObserver(this);
+  WmShell::Get()->AddDisplayObserver(this);
   UpdateDisplayInfo(NULL);
 }
 
 TrayDisplay::~TrayDisplay() {
-  Shell::GetInstance()->window_tree_host_manager()->RemoveObserver(this);
+  WmShell::Get()->RemoveDisplayObserver(this);
 }
 
 void TrayDisplay::UpdateDisplayInfo(TrayDisplay::DisplayInfoMap* old_info) {

ash/system/chromeos/tray_display.h

@@ -12,25 +12,21 @@
 #include "ash/ash_export.h"
 #include "ash/common/display/display_info.h"
 #include "ash/common/system/tray/system_tray_item.h"
-#include "ash/display/window_tree_host_manager.h"
+#include "ash/common/wm_display_observer.h"
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "ui/views/view.h"
 
 namespace ash {
-class DisplayView;
 
-namespace test {
-class AshTestBase;
-}
+class DisplayView;
 
-class ASH_EXPORT TrayDisplay : public SystemTrayItem,
-                               public WindowTreeHostManager::Observer {
+class ASH_EXPORT TrayDisplay : public SystemTrayItem, public WmDisplayObserver {
  public:
   explicit TrayDisplay(SystemTray* system_tray);
   ~TrayDisplay() override;
 
-  // Overridden from WindowTreeHostManagerObserver:
+  // Overridden from WmDisplayObserver:
   void OnDisplayConfigurationChanged() override;
 
  private:

ash/system/chromeos/tray_display_unittest.cc

@@ -6,7 +6,6 @@
 
 #include "ash/common/system/chromeos/devicetype_utils.h"
 #include "ash/display/display_manager.h"
-#include "ash/root_window_controller.h"
 #include "ash/screen_util.h"
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray.h"
@@ -126,8 +125,7 @@ TrayDisplay* TrayDisplayTest::GetTrayDisplay() {
 }
 
 void TrayDisplayTest::CheckUpdate() {
-  SystemTray* current =
-      Shell::GetPrimaryRootWindowController()->GetSystemTray();
+  SystemTray* current = GetPrimarySystemTray();
   if (tray_ != current) {
     tray_ = current;
     tray_display_ = new TrayDisplay(tray_);