Merge pull request #9631 from davidflanagan/bug833704

Bug 833704: don't regenerate poster image. r=daleharvey(cherry picked from commit f73e380ec94496707180aa8c4be0e87fdf65d9d2)
Merge pull request #9686 from davidflanagan/bug833704-v1-train

Merge pull request #9631 from davidflanagan/bug833704