Remove callers of deprecatedShadowAncestorNode

This patch removes callers of deprecatedShadowAncestorNode
from DragController and ReplaceSelectionCommand.

BUG=234099

Review URL: https://codereview.chromium.org/360733002

git-svn-id: svn://svn.chromium.org/blink/trunk@177633 bbb929c8-8fbe-4397-9dbb-9b2b20218538