Initializing Oxide should leave the UI thread GL state intact

[Chris Coulson]

During initialization of Oxide, it creates a couple of GL contexts and makes them current on the UI thread. However, it doesn't restore the previous UI thread GL state. This could be surprising for applications that instantiate the first instance of a WebView (or other class that triggers Oxide startup) and don't expect the GL state (eg, the current context) to change.