Bug 890743 - Display 0-delay, single loop GIFs instantly. r=seth

Do not artificially create a frame delay for GIF files
that do not loop and have an inter-frame delay of 0. Move timeout
calculation to FrameBlender and only access raw timeout of
imgFrame from within FrameBlender.

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extra : rebase_source : 1a568f16a2980d3d14621869c6b536d054088805