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

ui/base/ime/input_method_observer.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_BASE_IME_INPUT_METHOD_OBSERVER_H_
 #define UI_BASE_IME_INPUT_METHOD_OBSERVER_H_
 
 #include "ui/base/ime/ui_base_ime_export.h"
 
 namespace ui {
@@ skipping 11 matching lines @@
 
   // Called when the top-level system window gets keyboard focus. Currently
   // only used by the mock input method for testing.
   virtual void OnFocus() = 0;
 
   // Called when the top-level system window loses keyboard focus. Currently
   // only used by the mock input method for testing.
   virtual void OnBlur() = 0;
 
   // Called whenever the caret bounds is changed for the input client.
+  // Currently only used by the mock input method for testing.
   virtual void OnCaretBoundsChanged(const TextInputClient* client) = 0;
 
   // Called when either:
   //  - the TextInputClient is changed (e.g. by a change of focus)
   //  - the TextInputType of the TextInputClient changes
   virtual void OnTextInputStateChanged(const TextInputClient* client) = 0;
 
   // Called when the observed InputMethod is being destroyed.
   virtual void OnInputMethodDestroyed(const InputMethod* input_method) = 0;
 
   // Called when a user gesture should trigger showing the virtual keyboard
   // or alternate input view (e.g. handwriting palette). Used in ChromeOS.
   virtual void OnShowImeIfNeeded() = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_IME_INPUT_METHOD_OBSERVER_H_