Make the member |is_cursor_visible_| in DesktopWindowTreeHostWin static.

ui/views/widget/desktop_aura/desktop_root_window_host_win.h

Index: ui/views/widget/desktop_aura/desktop_root_window_host_win.h
diff --git a/ui/views/widget/desktop_aura/desktop_root_window_host_win.h b/ui/views/widget/desktop_aura/desktop_root_window_host_win.h
index 93b1a9c8709dc030f09954be521be5f50d8d2d4e..9e39ce92ac539419ed632fe66b1ba7c23911e0fd 100644
--- a/ui/views/widget/desktop_aura/desktop_root_window_host_win.h
+++ b/ui/views/widget/desktop_aura/desktop_root_window_host_win.h
@@ -273,8 +273,11 @@ class VIEWS_EXPORT DesktopWindowTreeHostWin
   // a reference.
   corewm::TooltipWin* tooltip_;
 
-  // State of the cursor.
-  bool is_cursor_visible_;
+  // Visibility of the cursor. On Windows we can have multiple root windows and
+  // the implementation of ::ShowCursor() is based on a counter, so making this
+  // member static ensures that ::ShowCursor() is always called exactly once
+  // whenever the cursor visibility state changes.
+  static bool is_cursor_visible_;
 
   scoped_ptr<aura::client::ScopedTooltipDisabler> tooltip_disabler_;