Stop showing "Replace" when selection isn't inside spans.

Currently, "Replace" is shown when any spans intersects
the selection. It causes confusing behavior when multiple
words are selected. "Replace" is in the ActionBar, but it's
unclear which word will be replaced. It can happen when
text is selected using long tap + drag, unig keyboard, or
using a mouse.

Bug: 19396964
Change-Id: I512f5f566d4060cd0aa7b28594054bf4f6bf7458