ash: Move VirtualKeyboardStateObserver functionality to ShellObserver

ash/shell/shell_delegate_impl.h

Index: ash/shell/shell_delegate_impl.h
diff --git a/ash/shell/shell_delegate_impl.h b/ash/shell/shell_delegate_impl.h
index ce80c0c03f4c5b003e1981ac30d72f96f292f433..404356734f54e6ed3629bc3f73b2f6b9469a8dde 100644
--- a/ash/shell/shell_delegate_impl.h
+++ b/ash/shell/shell_delegate_impl.h
@@ -9,7 +9,6 @@
 #include <string>
 
 #include "ash/common/shell_delegate.h"
-#include "base/compiler_specific.h"
 #include "base/macros.h"
 
 namespace app_list {
@@ -41,11 +40,6 @@ class ShellDelegateImpl : public ShellDelegate {
   void PreShutdown() override;
   void Exit() override;
   keyboard::KeyboardUI* CreateKeyboardUI() override;
-  void VirtualKeyboardActivated(bool activated) override;
-  void AddVirtualKeyboardStateObserver(
-      VirtualKeyboardStateObserver* observer) override;
-  void RemoveVirtualKeyboardStateObserver(
-      VirtualKeyboardStateObserver* observer) override;
   void OpenUrl(const GURL& url) override;
   app_list::AppListPresenter* GetAppListPresenter() override;
   ShelfDelegate* CreateShelfDelegate(ShelfModel* model) override;