[ash-md] Adds support for gesture to move selection in overview mode

ash/common/wm/overview/window_selector.h

Index: ash/common/wm/overview/window_selector.h
diff --git a/ash/common/wm/overview/window_selector.h b/ash/common/wm/overview/window_selector.h
index bb3f6d417088ef7326f40418600a82bf1041a31e..5512f4d89e89d595cabd0ec98c9bbea8c8451575 100644
--- a/ash/common/wm/overview/window_selector.h
+++ b/ash/common/wm/overview/window_selector.h
@@ -61,6 +61,14 @@ class ASH_EXPORT WindowSelector : public display::DisplayObserver,
   // Called when the last window selector item from a grid is deleted.
   void OnGridEmpty(WindowGrid* grid);
 
+  // Moves the current selection by |increment| items. Positive values of
+  // |increment| move the selection forward, negative values move it backward.
+  void IncrementSelection(int increment);
+
+  // Accepts current selection if any. Returns true if a selection was made,
+  // false otherwise.
+  bool AcceptSelection();
+
   // Activates |item's| window.
   void SelectWindow(WindowSelectorItem* item);