We currently use ComputedStyleRef in MediaControlOverlayPlayButtonElement::IsMouseEventOnInternalButton. This is called in KeepEventInNode for mouse events. In certain cases, ComputedStyleRef is crashing since ComputedStyle is null. For now, we're going to check that the computed style isn't null before making the call, but we should check to see what situation is causing this and make sure we're doing the right thing. See crbug.com/870490.