base

Many fixes to text input in the browser, particularly when moving to a new field.

Remove many instances where we are setting selection unnecessarily.  Instead, only
set the selection due to a click, touch, or inserting a character.  A touch will
now set the selection properly, rather than at the beginning/end, fixing
http://b/issue?id=1650395  Also fixes http://b/issue?id=2208188

Requires a change to external/webkit.