Added arrow key navigation to Overview Mode

ash/wm/overview/window_selector_item.h

Index: ash/wm/overview/window_selector_item.h
diff --git a/ash/wm/overview/window_selector_item.h b/ash/wm/overview/window_selector_item.h
index 7b2fcb80f090a153fa6b9fc572fffcb3938fbb3a..452632514af07caad384115cc912af0e95e2b055 100644
--- a/ash/wm/overview/window_selector_item.h
+++ b/ash/wm/overview/window_selector_item.h
@@ -72,6 +72,10 @@ class WindowSelectorItem {
   // dispatched when the bounds of a window change.
   void RecomputeWindowTransforms();
 
+  // Sends an a11y focus alert so that, if chromevox is enabled, the window
+  // label is read.
+  void SendFocusAlert() const;
+
   const gfx::Rect& bounds() { return bounds_; }
   const gfx::Rect& target_bounds() { return target_bounds_; }