Extract content dependency from keyboard code

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 4f0e3e435c8e6a7ea8ab40ada38f5701c232b910..acab4044f84ec4c2c9b9485460c9586beef4275b 100644
--- a/ash/shell/shell_delegate_impl.h
+++ b/ash/shell/shell_delegate_impl.h
@@ -11,7 +11,7 @@
 #include "base/compiler_specific.h"
 
 namespace keyboard {
-class KeyboardControllerProxy;
+class KeyboardUI;
 }
 
 namespace ash {
@@ -37,7 +37,7 @@ class ShellDelegateImpl : public ash::ShellDelegate {
   void PreInit() override;
   void PreShutdown() override;
   void Exit() override;
-  keyboard::KeyboardControllerProxy* CreateKeyboardControllerProxy() override;
+  keyboard::KeyboardUI* CreateKeyboardUI() override;
   void VirtualKeyboardActivated(bool activated) override;
   void AddVirtualKeyboardStateObserver(
       VirtualKeyboardStateObserver* observer) override;