--- a/gfx/layers/FrameMetrics.h
+++ b/gfx/layers/FrameMetrics.h
@@ -245,19 +245,16 @@ public:
   // Note that this is structured in such a way that it doesn't depend on the
   // method layout uses to scroll content.
   //
   // May be larger or smaller than |mScrollableRect|.
   //
   // To pre-render a margin of 100 CSS pixels around the window,
   // { x = -100, y = - 100,
   //   width = window.innerWidth + 200, height = window.innerHeight + 200 }
-  //
-  // This is only valid on the root layer. Nested iframes do not have a
-  // displayport set on them. See bug 775452.
   CSSRect mDisplayPort;
 
   // If non-empty, the area of a frame's contents that is considered critical
   // to paint. Area outside of this area (i.e. area inside mDisplayPort, but
   // outside of mCriticalDisplayPort) is considered low-priority, and may be
   // painted with lower precision, or not painted at all.
   //
   // The same restrictions for mDisplayPort apply here.