Create a new ImeOption that disables fullscreen in landscape, and use it.

EditorInfo:
Add a flag to tell the InputMethodService to never go into fullscreen
mode.

InputMethodService:
When the new flag is set, onEvaluateFullscreenMode always returns
false.

WebTextView:
Use the new flag, along with IME_FLAG_NO_EXTRACT_UI.  Fixes
http://b/issue?id=2358360