Disable VK overscroll for login/out-of-box.

ui/keyboard/keyboard_util.h

Index: ui/keyboard/keyboard_util.h
diff --git a/ui/keyboard/keyboard_util.h b/ui/keyboard/keyboard_util.h
index bc343bda7b654b5603977069bae1900296f97cc4..c3ef7aff3d90b4a392836ebf0eec12f2973fe8fb 100644
--- a/ui/keyboard/keyboard_util.h
+++ b/ui/keyboard/keyboard_util.h
@@ -38,6 +38,13 @@ enum KeyboardControlEvent {
   KEYBOARD_CONTROL_MAX,
 };
 
+// An enumeration of keyboard overscroll override value.
+enum KeyboardOverscrolOverride {
+  KEYBOARD_OVERSCROLL_OVERRIDE_DISABLED = 0,
+  KEYBOARD_OVERSCROLL_OVERRIDE_ENABLED,
+  KEYBOARD_OVERSCROLL_OVERRIDE_NONE,
+};
+
 // Gets the default keyboard bounds from |window_bounds|.
 KEYBOARD_EXPORT gfx::Rect DefaultKeyboardBoundsFromWindowBounds(
     const gfx::Rect& window_bounds);
@@ -71,6 +78,10 @@ KEYBOARD_EXPORT bool IsKeyboardUsabilityExperimentEnabled();
 // Returns true if keyboard overscroll mode is enabled.
 KEYBOARD_EXPORT bool IsKeyboardOverscrollEnabled();
 
+// Sets temporary keyboard overscroll override.
+KEYBOARD_EXPORT void SetKeyboardOverscrollOverride(
+    KeyboardOverscrolOverride override);
+
 // Returns true if an IME extension can specify a custom input view for the
 // virtual keyboard window.
 KEYBOARD_EXPORT bool IsInputViewEnabled();