Bug 845519 - Fix aliasing problem between Rooted<T> and Rooted<derived-from-T>. r=bhackett

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extra : rebase_source : 38e1a42e7408e6bd60dbdc42f2dbb5cffb68625d
Bug 845519 - Check getType(cx) return value (also fixes rooting hazard). r=bhackett

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extra : rebase_source : 3031e892cd93c36db9096e47fcb20fb3dc9913dc
Bug 845519 - Use SkipRoots for jschar pointers until we need to start moving them. r=terrence

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extra : rebase_source : d337dba6972e78e1994dd5563f093622e4475fc8
Bug 845519 - Spot-fix Unrooted-related problems. r=terrence

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extra : rebase_source : d725080582e51c4d6385b0adbb188933641988bd