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..e81be6b646cf5b1c151521afa745ceabe06de34c 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
@@ -14,6 +14,7 @@
 #include "ui/base/class_property.h"
 #include "ui/base/cursor/cursor_loader_win.h"
 #include "ui/base/ime/input_method.h"
+#include "ui/base/ime/input_method_observer.h"
 #include "ui/base/win/shell.h"
 #include "ui/compositor/compositor_constants.h"
 #include "ui/compositor/paint_context.h"
@@ -600,6 +601,16 @@ void DesktopWindowTreeHostWin::OnWindowHidingAnimationCompleted() {
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopWindowTreeHostWin, HWNDMessageHandlerDelegate implementation:
 
+void DesktopWindowTreeHostWin::AddInputMethodObserver(
+    ui::InputMethodObserver* observer) {
+  GetInputMethod()->AddObserver(observer);
+}
+
+void DesktopWindowTreeHostWin::RemoveInputMethodObserver(
+    ui::InputMethodObserver* observer) {
+  GetInputMethod()->RemoveObserver(observer);
+}
+
 bool DesktopWindowTreeHostWin::HasNonClientView() const {
   return has_non_client_view_;
 }