Added a system caret used for accessibility on Windows.

ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc b/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
index 8295d4dae10fdc1cd8e7108f21632aba8987f876..93939674a9c508fc468a904f1aedb358e1355145 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
@@ -600,6 +600,10 @@ void DesktopWindowTreeHostWin::OnWindowHidingAnimationCompleted() {
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopWindowTreeHostWin, HWNDMessageHandlerDelegate implementation:
 
+ui::InputMethod* DesktopWindowTreeHostWin::GetHWNDMessageDelegateInputMethod() {
+  return GetInputMethod();
+}
+
 bool DesktopWindowTreeHostWin::HasNonClientView() const {
   return has_non_client_view_;
 }