Bug 928607. Ensure that nsGfxScrollFrameInner::UpdatePosition clips the overflow area of its children. r=tn

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extra : rebase_source : 2c8e33393cf73b6760cd26017c58a44d209b8e9b
Backed out changeset 673ca84a9171 because of wrong bug number in commit message

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extra : rebase_source : 32c92c4cb98097caf8805fdae98d9c435580c8c9
Bug 754356: Remove TLS intolerance timeout logic, r=honzab

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extra : rebase_source : 49c4563800ce9727e11e08d857db44c1294a074b