Bug 888768 (part 2) - Remove frontend/SharedContext-inl.h.  r=till.

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extra : rebase_source : d9bb2d56d54eed908a8d9301519866bd417321df
Bug 888768 (part 3) - Remove unnecessary *-inl.h #includes, as found by include-what-you-use.  r=till.

--HG--
extra : rebase_source : 74b89e7ed7d9279061d88b29fff8e9c50c3a0050