Fix crash with a11y set text with text filters.

A text filter may shorten the text, so we need to use the text
that's actually in the View, not the text we requested, to move
the selection.

Also removing the override of performAccessibilityActionInternal,
which should have been done as part of adding text actions initially.

Bug: 28253708
Change-Id: I184f49dcba0238f4ccc222597cefca258393b263