Bug 880041 (part 20) - Use JSObject::{is,as} for {Map,Set}Object.  r=sfink.

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extra : rebase_source : d5ba2f1cce67ac72bb3cd1c036b93fa3694745a7
Bug 880041 (part 21) - Use JSObject::{is,as} for GlobalObject.  r=sfink.

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extra : rebase_source : 676539d76be0aee1c5450aacefed27a4f45efc81
Bug 880041 (part 22) - Use JSObject::{is,as} for JSFunction.  r=sfink.

--HG--
extra : rebase_source : 43c8c65c7d00edffde12c5b1ec8a1aff42acc7fe