Implement overscroll support for the virtual keyboard.

ui/keyboard/keyboard_util.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_KEYBOARD_KEYBOARD_UTIL_H_
 #define UI_KEYBOARD_KEYBOARD_UTIL_H_
 
 #include <string>
 
 #include "base/strings/string16.h"
@@ skipping 45 matching lines @@
 
 // Gets the default keyboard layout.
 KEYBOARD_EXPORT std::string GetKeyboardLayout();
 
 // Returns true if the virtual keyboard is enabled.
 KEYBOARD_EXPORT bool IsKeyboardEnabled();
 
 // Returns true if the keyboard usability test is enabled.
 KEYBOARD_EXPORT bool IsKeyboardUsabilityExperimentEnabled();
 
+// Returns true if keyboard overscroll mode is enabled.
+KEYBOARD_EXPORT bool IsKeyboardOverscrollEnabled();
+
 // Returns true if an IME extension can specify a custom input view for the
 // virtual keyboard window.
 KEYBOARD_EXPORT bool IsInputViewEnabled();
 
 // Insert |text| into the active TextInputClient associated with |root_window|,
 // if there is one. Returns true if |text| was successfully inserted. Note
 // that this may convert |text| into ui::KeyEvents for injection in some
 // special circumstances (i.e. VKEY_RETURN, VKEY_BACK).
 KEYBOARD_EXPORT bool InsertText(const base::string16& text,
                                 aura::Window* root_window);
@@ skipping 37 matching lines @@
 
 // Gets the override content url.
 KEYBOARD_EXPORT const GURL& GetOverrideContentUrl();
 
 // Logs the keyboard control event as a UMA stat.
 void LogKeyboardControlEvent(KeyboardControlEvent event);
 
 }  // namespace keyboard
 
 #endif  // UI_KEYBOARD_KEYBOARD_UTIL_H_