previously failures in the call to
VP8LBackwardReferencesTraceBackwards() would be ignored which, though it
wouldn't result in a crash, would produce non-deterministic output
Change-Id: Id9890a60883c3270ec75e968506d46eea32b76d4
(cherry picked from commit e3cfafaf71)
(cherry picked from commit 20ef03ee35)
(cherry picked from commit 89e226a3c7)