Add ability to have active window autohide shelf

ash/wm/window_util.h

Index: ash/wm/window_util.h
diff --git a/ash/wm/window_util.h b/ash/wm/window_util.h
index 589fae482e662013baa83fbc5ef02a99a862cd7b..7def41561f269eaf5b24986418da9785d9852013 100644
--- a/ash/wm/window_util.h
+++ b/ash/wm/window_util.h
@@ -43,6 +43,10 @@ ASH_EXPORT bool IsWindowUserPositionable(aura::Window* window);
 // Pins the window on top of other windows.
 ASH_EXPORT void PinWindow(aura::Window* window, bool trusted);
 
+// Indicates that the window should autohide the shelf when it is the active
+// window.
+ASH_EXPORT void SetAutoHideShelf(aura::Window* window, bool autohide);
+
 // Moves |window| to the root window for the given |display_id|, if it is not
 // already in the same root window. Returns true if |window| was moved.
 ASH_EXPORT bool MoveWindowToDisplay(aura::Window* window, int64_t display_id);