Allow moving cursors between connected displays.

ash/display/unified_mouse_warp_controller.cc

Index: ash/display/unified_mouse_warp_controller.cc
diff --git a/ash/display/unified_mouse_warp_controller.cc b/ash/display/unified_mouse_warp_controller.cc
index 267f2f53f17e40ce83736b874e35ce961e8e69e3..fec9b6044af0094772c21dbd11ddecc6c5823fad 100644
--- a/ash/display/unified_mouse_warp_controller.cc
+++ b/ash/display/unified_mouse_warp_controller.cc
@@ -131,8 +131,9 @@ void UnifiedMouseWarpController::ComputeBounds() {
 
   const gfx::Display& first = display_list[0];
   const gfx::Display& second = display_list[1];
-  ComputeBoundary(first, second, &first_edge_bounds_in_native_,
-                  &second_edge_bounds_in_native_);
+  bool success = ComputeBoundary(first, second, &first_edge_bounds_in_native_,
+                                 &second_edge_bounds_in_native_);
+  DCHECK(success);
 
   first_edge_bounds_in_native_ =
       GetNativeEdgeBounds(GetMirroringAshWindowTreeHostForDisplayId(first.id()),