Bug 1039861: Remove the last bits of OS.File from apps code. r=fabrice

After this patch OS.File is not loaded in content processes anymore.

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extra : rebase_source : 64d41fa57e1265dee501e7919eaea5d733320cad
Bug 1040380: Report the size of text nodes in the CC graph. r=smaug

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extra : rebase_source : bfb7217a8e617709e6f0a8e95d41563fdbd65959