Merge pull request #11202 from davidflanagan/bug896907

Bug 896907: let the user preview a captured video before picking it r=daleharvey,johnhu(cherry picked from commit 862de8489b648a9af7e8a5b88be031b5479404ba)

Conflicts:

	apps/camera/js/camera.js
	apps/camera/style/filmstrip.css
Merge pull request #11278 from davidflanagan/bug896907-v1-train

Bug896907 v1 train