[Android] New Embedding API

This commit implements onCreateWindowRequested of XWalkView
Also fixed the type error when generating some wrapper interface
Suppose the handling is in `setNativeContent`. But not for session saving and resuming. it's not guaranteed that parent view will become invisible, it's probably embedders' duty to decide whether call `onHide` of parent view depends on how they are handing the UI transition. For the child view here, calling `onShow()` for it is reasonable since we do the same thing for the normal created XWalkView too.