When clicking on a WebTextView, always call nativeMotionUp.

We were previously calling nativeTextInputMotionUp, which was
intended to be faster than nativeMotionUp, which does more work.
However, as discussed in http://b/issue?id=2257787 , I think we
should simply call nativeMotionUp, which does everything the old
method did, while also correcting things if necessary.  This fixes
the second problem listed in http://b/issue?id=2266756 , since
nativeMotionUp will recognize that the <select> element should
take the click.

Since I have removed a native method, this requires a change to
external/webkit.