Bug 983538 (part 1) - Convert mfbt/SplayTree.h to Mozilla style. r=froydnj.

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extra : rebase_source : 9143ee56f94e7c6e0b1e1a70c4dc26c90c69d84a
Bug 983538 (part 2) - Update mfbt/STYLE. r=froydnj.

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extra : rebase_source : dac8a5683794cc838966afaf8c037aa466d44410