Bug 1349293, part 1 - Prevent UnionBorderBoxes from processing NS_FRAME_IS_NONDISPLAY frames. r=mattwoodrow

MozReview-Commit-ID: EDGd5sJo5E2

layout/generic/nsFrame.cpp

@@ -8703,9 +8703,14 @@ UnionBorderBoxes(nsIFrame* aFrame, bool aApplyTransform,
   aOutValid = !aFrame->IsFrameOfType(nsIFrame::eSVGContainer)
               || aFrame->GetType() == nsGkAtoms::svgTextFrame;
 
+  nsRect u;
+
+  if (!aFrame->FrameMaintainsOverflow()) {
+    return u;
+  }
+
   // Start from our border-box, transformed.  See comment below about
   // transform of children.
-  nsRect u;
   bool doTransform = aApplyTransform && aFrame->IsTransformed();
   if (doTransform) {
     u = nsDisplayTransform::TransformRect(bounds, aFrame, &bounds);