Web Player のセキュリティが有効になっているか確認する。
In the web player, this will always return true.
In the Unity editor, it will return true if web security emulation is enabled (Menu->Edit->Project Settings->Editor) and false if the emulation is disabled.
On all other platforms, this will return false;
This property can only be read. You can use EditorSettings.webSecurityEmulationEnabled to set this setting in the editor environment.
Note: The web player is not supported from 5.4.0 onwards.