Add ink drop ripple to overview mode button

ash/common/wm/overview/window_selector_controller.h

Index: ash/common/wm/overview/window_selector_controller.h
diff --git a/ash/common/wm/overview/window_selector_controller.h b/ash/common/wm/overview/window_selector_controller.h
index a8318609fb6015d627d7396f6d09a470621c220b..3254a3702ba1dff8984f20e709133eb2a41eba17 100644
--- a/ash/common/wm/overview/window_selector_controller.h
+++ b/ash/common/wm/overview/window_selector_controller.h
@@ -30,10 +30,9 @@ class ASH_EXPORT WindowSelectorController : public WindowSelectorDelegate {
   // at certain times, such as when the lock screen is visible.
   static bool CanSelect();
 
-  // Enters overview mode. This is essentially the window cycling mode however
-  // not released on releasing the alt key and allows selecting with the mouse
-  // or touch rather than keypresses.
-  void ToggleOverview();
+  // Attempts to toggle overview mode and returns true if successful (showing
+  // overview would be unsuccessful if there are no windows to show).
+  bool ToggleOverview();
 
   // Returns true if window selection mode is active.
   bool IsSelecting() const;