Bug 879079 - Make ToNumber take a Handle to fix some static rooting analysis failures; r=sfink

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extra : rebase_source : 048d46820baedeb593f85e0d445375d482d16050
Bug 879079 - Fix some static root analysis failures; r=sfink

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extra : rebase_source : 40407ff41a7380fc4107958a7e4af843c826301f