REGRESSION (WK2): Tapping on the input field in duckduckgo.com shows the keyboard but not the caret.
https://bugs.webkit.org/show_bug.cgi?id=133140
<rdar://problem/16980898>

Reviewed by Benjamin Poulain.

When a page focuses a field on load, we receive the call to startAssistingNode
but we don't create a text interaction assistant if the focus is not originated
by a user action. Upon receiving the selection change notification we don't
call the text interaction assistant, since we don't have one, but we do call
the web selection assistant. We don't have any valid rects for web selection
and we clear the selection on the page, causing the caret not to appear and
the typing to have no effect.

* UIProcess/ios/WKContentViewInteraction.mm:
(-[WKContentView _updateChangedSelection]):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@169142 268f45cc-cd09-0410-ab3c-d52691b4dbfc