Bug 1067721 - [e10s] Make "Save Snapshot As" context menu item work for e10s. r=felipe.

--HG--
rename : browser/base/content/test/general/bug564387.html => browser/base/content/test/general/web_video.html
rename : browser/base/content/test/general/bug564387_video1.ogv => browser/base/content/test/general/web_video1.ogv
rename : browser/base/content/test/general/bug564387_video1.ogv^headers^ => browser/base/content/test/general/web_video1.ogv^headers^
extra : rebase_source : 1c2fad8158ef3803d653014d7dc1c8ce022dfc40