Bug 923151 - Part 1: Don't #include nsIDocument.h in TabChild.h; r=jst

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extra : rebase_source : 1748c347eeed09a8216580a48dd786f0dbe92588
Bug 923151 - Part 2: Don't #include nsIDocument.h in mozilla/dom/Element.h; r=jst

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extra : rebase_source : 8c5f5429574313a1304eb2779cdb6b5702e4094d