Implement overscroll support for the virtual keyboard.

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 a3a1f8a9bfd317c1b3c99147427ee63fd9a047b7..ca30c79ca5fa44bdc63f95f71896c4a989cd4200 100644
--- a/ui/keyboard/keyboard_util.h
+++ b/ui/keyboard/keyboard_util.h
@@ -63,6 +63,9 @@ 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();

[James Cook, 2014/04/15 17:54:10]

Not for this CL but Ash uses functions with names like UseFeatureFoo() instead
of IsFeatureFooEnabled().  See ash_switches.h.  It would be nice to standardize
on one convention or the other.

+
 // Returns true if an IME extension can specify a custom input view for the
 // virtual keyboard window.
 KEYBOARD_EXPORT bool IsInputViewEnabled();