Bug 875175 - Stop continuous reflow and invalidation of entire SVG when an element that is partially/wholly outside the viewport is subject to a transform animation. r=dbaron
Bug 855221 - Don't flush from imgFrame::ImageUpdated(), which can be called from the decoder thread. r=jrmuizel

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extra : rebase_source : a52a6ed8dc4d0477593f0af8289bb14a61594a3a