Cherry-pick Ib76a95d9e7669016cf11b8b0add8843b438068ea from gingerbread

DO NOT MERGE Fix bug 3121030 - Text handles erroneously appear over
extract mode IME window

Make the SelectionModifierCursorController track its show/hide state
more accurately in the presence of an extract mode IME.

Lazily initialize CursorControllers so that we don't end up creating
them for various TextViews where they are not needed.

Change-Id: I3dce7535db3a1bd25ed9899406de47b00058e665