Previously, automatic hyphenation blindly took almost every line
breaking opportunity as a word break, so words like "low-budget" were
treated as two separate words, "low-", and "budget", each
automatically hyphenated.

This patch makes sure the subwords in already-hyphenated phrases are
not passed to the automatic hyphenator, while keeping the possibility
of a potential line break where a hyphen already exists.

Bug: 22484266
Bug: 22287425
Change-Id: Ie46dbdd70e993d64a9b9cf44b4ae93b21459dbc2