IME events are now dispatched to native applications.

And also:

- APIs to show and hide the IME, and control its interaction with the app.
- APIs to tell the app when its window resizes and needs to be redrawn.
- API to tell the app the content rectangle of its window (to layout
  around the IME or status bar).

There is still a problem with IME interaction -- we need a way for the
app to deliver events to the IME before it handles them, so that for
example the back key will close the IME instead of finishing the app.

Change-Id: I37b75fc2ec533750ef36ca3aedd2f0cc0b5813cd