Revert of Added a system caret used for accessibility on Windows.

ui/views/widget/desktop_aura/desktop_window_tree_host_win.h

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_win.h b/ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
index 3f1c7bffb61f426973561042ff4f9dcb57266b5c..6099dc14adcae1bd2da71e88050a4607f7ec8ed9 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
@@ -19,13 +19,9 @@
 }
 }
 
-namespace ui {
-class InputMethod;
-}  // namespace ui
-
 namespace wm {
 class ScopedTooltipDisabler;
-}  // namespace wm
+}
 
 namespace views {
 class DesktopDragDropClientWin;
@@ -139,7 +135,6 @@
   void OnWindowHidingAnimationCompleted() override;
 
   // Overridden from HWNDMessageHandlerDelegate:
-  ui::InputMethod* GetHWNDMessageDelegateInputMethod() override;
   bool HasNonClientView() const override;
   FrameMode GetFrameMode() const override;
   bool HasFrame() const override;