Bug 1052491, part 2 - In jsinfer, support symbol jsids. r=bhackett. This should fix symbol-related orange on a CLOSED TREE.

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extra : rebase_source : 2dbdd4ec819c14627c9a5f081c83e4afb56b6d6c
extra : amend_source : baed01f715df89f4bef993902d030164b990506f