Avoid requiring a recalc to update compositing state for iframes

LayoutTests/platform/win/fast/repaint/line-flow-with-floats-2-expected.txt

Index: LayoutTests/platform/win/fast/repaint/line-flow-with-floats-2-expected.txt
diff --git a/LayoutTests/platform/win/fast/repaint/line-flow-with-floats-2-expected.txt b/LayoutTests/platform/win/fast/repaint/line-flow-with-floats-2-expected.txt
index f3fde0d84cb8ca330f123dddb06ebba7e093757f..1eb09fc99b82823ebf02eb378e8b04fcce09f509 100644
--- a/LayoutTests/platform/win/fast/repaint/line-flow-with-floats-2-expected.txt
+++ b/LayoutTests/platform/win/fast/repaint/line-flow-with-floats-2-expected.txt
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