Moves maintaining ShellObservers back to Shell

ash/accelerators/accelerator_interactive_uitest_chromeos.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/common/accelerators/accelerator_controller.h"
 
 #include "ash/common/shell_observer.h"
 #include "ash/common/system/chromeos/network/network_observer.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/common/system/tray/system_tray_notifier.h"
@@ skipping 44 matching lines @@
 // using ui_controls::Send*() functions.
 // This is to catch any future regressions (crbug.com/469235).
 class AcceleratorInteractiveUITest : public AshInteractiveUITestBase,
                                      public ShellObserver {
  public:
   AcceleratorInteractiveUITest() : is_in_overview_mode_(false) {}
 
   void SetUp() override {
     AshInteractiveUITestBase::SetUp();
 
-    WmShell::Get()->AddShellObserver(this);
+    Shell::GetInstance()->AddShellObserver(this);

[msw, 2017/03/08 19:52:23]

tangential: wdyt about adding Shell::Get and phasing out GetInstance?

[sky, 2017/03/08 20:26:06]

+1 will do it separately.

 
     chromeos::NetworkHandler::Initialize();
   }
 
   void TearDown() override {
     chromeos::NetworkHandler::Shutdown();
 
-    WmShell::Get()->RemoveShellObserver(this);
+    Shell::GetInstance()->RemoveShellObserver(this);
 
     AshInteractiveUITestBase::TearDown();
   }
 
   // Sends a key press event and waits synchronously until it's completely
   // processed.
   void SendKeyPressSync(ui::KeyboardCode key,
                         bool control,
                         bool shift,
                         bool alt) {
@@ skipping 123 matching lines @@
   SendKeyPressSync(ui::VKEY_LWIN, false, false, false);
   RunAllPendingInMessageLoop();
   EXPECT_EQ(1u, test_app_list_presenter.toggle_count());
   SendKeyPressSync(ui::VKEY_LWIN, false, false, false);
   RunAllPendingInMessageLoop();
   EXPECT_EQ(2u, test_app_list_presenter.toggle_count());
 }
 
 }  // namespace test
 }  // namespace ash