Add in gesture for immersive mode

ash/root_window_controller.h

Index: ash/root_window_controller.h
diff --git a/ash/root_window_controller.h b/ash/root_window_controller.h
index ea3f316e4da85cdb325db045ad12168f02209de5..aea518d1bd67644646d909858d052e4a0523196c 100644
--- a/ash/root_window_controller.h
+++ b/ash/root_window_controller.h
@@ -169,6 +169,11 @@ class ASH_EXPORT RootWindowController {
   // so clients of Ash don't need to know the details of workspace management.
   bool IsImmersiveMode() const;
 
+  // Sets kPendingImmersiveGestureKey if the active workspace is in immersive
+  // mode. Exposed here so clients of Ash don't need to know the details of
+  // workspace management.
+  void SetPendingImmersiveGesture(bool vlaue);
+
  private:
   // Creates each of the special window containers that holds windows of various
   // types in the shell UI.