map keyboard for webview

Treat the numeric keypad enter as the regular enter for the
purposes of completing a text entry or activating the currently
selected link.

Add a little keyboard-related debugging.

Don't call select text to extend the selection if the tap
point hasn't moved.

A separate change to the Browser app adds more keyboard
accelerators.

bug:3270434
bug:3191699
Change-Id: I8a38b26196e93e344dc2a4b39a6968fe0c158d47